diff --git a/src/bin/10_regular_expression_matching.rs b/src/bin/10_regular_expression_matching.rs
deleted file mode 100644
index 19f173d..0000000
--- a/src/bin/10_regular_expression_matching.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-fn main() {
-    println!("{}", is_match(String::from("acaabbaccbbacaabbbb"), String::from("a*.*b*.*a*aa*a*")))
-}
-
-pub fn is_match(s: String, p: String) -> bool {
-    let (s, p) = (s.as_bytes(), p.as_bytes());
-    let mut dp = vec![vec![false; p.len() + 1]; s.len() + 1];
-    dp[s.len()][p.len()] = true;
-    for i in (0..=s.len()).rev() {
-        for j in (0..p.len()).rev() {
-            let first_match = i < s.len() && (p[j] == b'.' || p[j] == s[i]);
-            if j + 1 < p.len() && p[j + 1] == b'*' {
-                dp[i][j] = first_match && dp[i + 1][j] || dp[i][j + 2];
-                continue;
-            }
-            dp[i][j] = first_match && dp[i + 1][j + 1];
-        }
-    }
-    return dp[0][0];
-}
diff --git a/src/bin/11_container_with_most_water.rs b/src/bin/11_container_with_most_water.rs
deleted file mode 100644
index 5937f31..0000000
--- a/src/bin/11_container_with_most_water.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-fn main() {
-    println!("{}", max_area(vec![1,8,6,2,5,4,8,3,7]));
-}
-
-pub fn max_area(height: Vec<i32>) -> i32 {
-    let (mut left, mut right) = (0, height.len() - 1);
-    let mut max_water = 0;
-    while left < right {
-        let x = (right - left) as i32; let h;
-        if height[left] < height[right] {
-            h = height[left];
-            left += 1;
-        } else {
-            h = height[right];
-            right -= 1;
-        };
-        max_water = max_water.max(h * x);
-    }
-    return max_water;
-}
diff --git a/src/bin/12_integer_to_roman.rs b/src/bin/12_integer_to_roman.rs
deleted file mode 100644
index 58a44bf..0000000
--- a/src/bin/12_integer_to_roman.rs
+++ /dev/null
@@ -1,35 +0,0 @@
-fn main() {
-    println!("{}", int_to_roman(1994));
-}
-
-pub fn int_to_roman(num: i32) -> String {
-    let roman_nums = vec!['M', 'D', 'C', 'L', 'X', 'V', 'I'];
-    let mut result = String::with_capacity(15);
-    let (mut num, mut divisor) = (num, 1000);
-    for i in (0..roman_nums.len()).step_by(2) {
-        let roman = roman_nums[i];
-        let roman_amount = num / divisor;
-        match roman_amount {
-            0 => (),
-            1..=3 => {
-                for _ in 0..roman_amount { result.push(roman); }
-            },
-            5..=8 => {
-                let complement = roman_nums[i - 1];
-                result.push(complement);
-                for _ in 0..(roman_amount-5) { result.push(roman); }
-            },
-            4 | 9 => {
-                let complement_index = i - roman_amount as usize / 4; 
-                let complement = roman_nums[complement_index];
-                result.push(roman);
-                result.push(complement);
-            },
-            _ => ()
-        }
-        num %= divisor;
-        divisor /= 10;
-    }
-    if result.is_empty() { result.push('0'); }
-    return result;
-}
diff --git a/src/bin/13_roman_to_integer.rs b/src/bin/13_roman_to_integer.rs
deleted file mode 100644
index c345340..0000000
--- a/src/bin/13_roman_to_integer.rs
+++ /dev/null
@@ -1,13 +0,0 @@
-fn main() {
-    println!("{}",  roman_to_int(String::from("MCMXCIV")));
-}
-
-pub fn roman_to_int(s: String) -> i32 {
-    s.chars().fold(0, |acc, c| {
-        let num = match c {
-            'M' => 1000, 'D' => 500, 'C' => 100, 'L' => 50,
-            'X' => 10, 'V' => 5, 'I' => 1, _ => 0
-        };
-        acc + num - 2 * (acc % num)
-    })
-}
diff --git a/src/bin/14_longest_common_prefix.rs b/src/bin/14_longest_common_prefix.rs
deleted file mode 100644
index c1f1d99..0000000
--- a/src/bin/14_longest_common_prefix.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-fn main() {
-
-}
-
-pub fn longest_common_prefix(strs: Vec<String>) -> String {
-    let mut result = String::with_capacity(200);
-    let first_str = strs[0].as_bytes();
-    if first_str.is_empty() { return result; }
-    for i in 0..first_str.len() {
-        let c = first_str[i];
-        for j in 1..strs.len() {
-            if i >= strs[j].len() || c != strs[j].as_bytes()[i] {
-                return result;
-            }
-        }
-        result.push(c as char);
-    }
-    return result;
-}
diff --git a/src/bin/15_3sum.rs b/src/bin/15_3sum.rs
deleted file mode 100644
index 27f0fd2..0000000
--- a/src/bin/15_3sum.rs
+++ /dev/null
@@ -1,31 +0,0 @@
-fn main() {
-    println!("{:?}", three_sum(vec![-1,0,1,2,-1,-4]));
-    println!("{:?}", three_sum(vec![0,0,0,0,0,0]));
-    println!("{:?}", three_sum(vec![-2,0,0,2,2]));
-}
-
-pub fn three_sum(mut nums: Vec<i32>) -> Vec<Vec<i32>> {
-    let mut result = Vec::<Vec<i32>>::new();
-    nums.sort();
-    for i in 0..nums.len()-2 {
-        if i > 0 && nums[i] == nums[i - 1] { continue; }
-        let (mut j, mut k) = (i + 1, nums.len() - 1);
-        while j < k {
-            if j > i + 1 && nums[j - 1] == nums[j] {
-                j += 1; continue;
-            }
-            if k < nums.len() - 1 && nums[k + 1] == nums[k] {
-                k -= 1; continue;
-            }
-            match (nums[i] + nums[j] + nums[k]).cmp(&0) {
-                std::cmp::Ordering::Less => { j += 1; },
-                std::cmp::Ordering::Greater => { k -= 1 },
-                std::cmp::Ordering::Equal => {
-                    result.push(vec![nums[i], nums[j], nums[k]]);
-                    j += 1; k -= 1;
-                }
-            }
-        }
-    }
-    return result;
-}
diff --git a/src/bin/16_3sum_closest.rs b/src/bin/16_3sum_closest.rs
deleted file mode 100644
index ac71fee..0000000
--- a/src/bin/16_3sum_closest.rs
+++ /dev/null
@@ -1,8 +0,0 @@
-fn main() {
-
-}
-
-pub fn three_sum_closest(nums: Vec<i32>, target: i32) -> i32 {
-    
-    return 0;
-}
diff --git a/src/bin/1_two_sum.rs b/src/bin/1_two_sum.rs
deleted file mode 100644
index 1eb1415..0000000
--- a/src/bin/1_two_sum.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-use std::collections::HashMap;
-
-fn main() {
-    println!("{:?}", two_sum(vec![2,7,11,15], 9));
-}
-
-pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
-    let mut components: HashMap<i32, usize> = HashMap::new();
-    for i in 0..nums.len() {
-        let component = target - nums[i];
-        if let Some(j) = components.get(&component) {
-            return vec![i as i32, *j as i32];
-        }
-        components.insert(nums[i], i);
-    }
-    return Vec::new();
-}
diff --git a/src/bin/2_add_two_numbers.rs b/src/bin/2_add_two_numbers.rs
deleted file mode 100644
index f0997eb..0000000
--- a/src/bin/2_add_two_numbers.rs
+++ /dev/null
@@ -1,46 +0,0 @@
-fn main() {
-    
-}
-
-pub fn add_two_numbers(l1: Option<Box<ListNode>>, l2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
-    let (mut l1, mut l2) = (l1, l2);
-    let mut head = Box::new(ListNode::new(0));
-    let mut tail = &mut head;
-    loop {
-        let mut sum = tail.val;
-        if let Some(node) = &l1 {
-            sum += node.val;
-            l1 = node.next.clone();
-        }
-        if let Some(node) = &l2 {
-            sum += node.val;
-            l2 = node.next.clone();
-        }
-        let next_node = Box::new(ListNode::new(sum / 10));
-        tail.val = sum % 10;
-        if l1.is_none() && l2.is_none() {
-            if next_node.val > 0 { tail.next = Some(next_node); }
-            break;
-        }
-        tail.next = Some(next_node);
-        tail = tail.next.as_mut().unwrap();
-    }
-    return Some(head);
-}
-
-// Definition for singly-linked list.
-#[derive(PartialEq, Eq, Clone, Debug)]
-pub struct ListNode {
-    pub val: i32,
-    pub next: Option<Box<ListNode>>
-}
-
-impl ListNode {
-    #[inline]
-    fn new(val: i32) -> Self {
-        ListNode {
-            next: None,
-            val
-        }
-    }
-}
diff --git a/src/bin/3_longest_substring_without_repeating_characters.rs b/src/bin/3_longest_substring_without_repeating_characters.rs
deleted file mode 100644
index 6abc5f5..0000000
--- a/src/bin/3_longest_substring_without_repeating_characters.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-use std::collections::HashMap;
-
-fn main() {
-    println!("{}", length_of_longest_substring(String::from("abcabcbb")));
-}
-
-pub fn length_of_longest_substring(s: String) -> i32 {
-    let mut seen: HashMap<char, usize> = HashMap::with_capacity(80);
-    let (mut start_index, mut max_length) = (0usize, 0usize);
-    for (i, c) in s.chars().enumerate() {
-        if let Some(index) = seen.get(&c) {
-            max_length = max_length.max(i - start_index);
-            start_index = *index + 1;
-            seen.retain(|_, i| *i >= start_index);
-        }
-        seen.insert(c, i);
-    }
-    max_length = max_length.max(s.len() - start_index);
-    return max_length as i32;
-}
diff --git a/src/bin/4_median_of_two_sorted_arrays.rs b/src/bin/4_median_of_two_sorted_arrays.rs
deleted file mode 100644
index c7b1f09..0000000
--- a/src/bin/4_median_of_two_sorted_arrays.rs
+++ /dev/null
@@ -1,22 +0,0 @@
-fn main() {
-
-}
-
-// TODO: reduce algorithm complexity from O(m+n) to O(log(m+n))
-pub fn find_median_sorted_arrays(nums1: Vec<i32>, nums2: Vec<i32>) -> f64 {
-    let length = nums1.len() + nums2.len();
-    let mut nums3 = vec![0i32; length];
-    let (mut m, mut n) = (0usize, 0usize);
-    while m + n < length {
-        let x1 = if m < nums1.len() { nums1[m] } else { i32::MAX };
-        let x2 = if n < nums2.len() { nums2[n] } else { i32::MAX };
-        if x1 <= x2 {
-            nums3[m + n] = x1;
-            m += 1;
-        } else {
-            nums3[m + n] = x2;
-            n += 1;
-        }
-    }
-    return (nums3[(length - 1) / 2] + nums3[length / 2]) as f64 / 2.0;
-}
diff --git a/src/bin/5_longest_palindrome_substring.rs b/src/bin/5_longest_palindrome_substring.rs
deleted file mode 100644
index 07897de..0000000
--- a/src/bin/5_longest_palindrome_substring.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-fn main() {
-    println!("{}", longest_palindrome(String::from("bb")));
-}
-
-pub fn longest_palindrome(s: String) -> String {
-    let mut max_indexes = (0usize, 1usize);
-    for i in 0..(s.len()-1)*2 {
-        let (mut start, mut end) = (i / 2 + i % 2, i / 2);
-        while start > 0 && end < s.len() - 1 {
-            if s.as_bytes()[start - 1] != s.as_bytes()[end + 1] { break; }
-            start -= 1; end += 1;
-        }
-        let length = end + 1 - start;
-        if length > max_indexes.1 - max_indexes.0 { max_indexes = (start, end + 1); }
-    }
-    return String::from(&s[max_indexes.0..max_indexes.1]);
-}
diff --git a/src/bin/6_zigzag_conversion.rs b/src/bin/6_zigzag_conversion.rs
deleted file mode 100644
index 414175b..0000000
--- a/src/bin/6_zigzag_conversion.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-fn main() {
-    println!("{}", convert(String::from("ABC"), 4))
-}
-
-pub fn convert(s: String, num_rows: i32) -> String {
-    if num_rows <= 1 { return s; }
-    let mut result = String::with_capacity(s.len());
-    let num_rows = num_rows as usize;
-    for i in 0..num_rows {
-        for j in (i..s.len()).step_by(num_rows * 2 - 2) {
-            result.push(s.as_bytes()[j] as char);
-            if i > 0 && i < num_rows - 1 {
-                let diagonal_index = j + 2 * (num_rows - i - 1);
-                if diagonal_index >= s.len() { continue; }
-                result.push(s.as_bytes()[diagonal_index] as char);
-            }
-        }
-    }
-    return result;
-}
diff --git a/src/bin/7_reverse_integer.rs b/src/bin/7_reverse_integer.rs
deleted file mode 100644
index 4a9713f..0000000
--- a/src/bin/7_reverse_integer.rs
+++ /dev/null
@@ -1,19 +0,0 @@
-fn main() {
-    println!("{}", reverse(1534236469));
-}
-
-// problem doesn't allow using 64-bit numbers
-pub fn reverse(x: i32) -> i32 {
-    let is_negative = x < 0;
-    let (mut x, mut result) = (x.checked_abs().unwrap_or(0), 0i32);
-    while x > 9 {
-        result *= 10;
-        result += x % 10;
-        x /= 10;
-    }
-    return result.checked_mul(10).and_then(|mut n| {
-        n += x % 10;
-        if is_negative { n = -n; }
-        Some(n)
-    }).unwrap_or(0);
-}
diff --git a/src/bin/8_string_to_integer.rs b/src/bin/8_string_to_integer.rs
deleted file mode 100644
index 673a183..0000000
--- a/src/bin/8_string_to_integer.rs
+++ /dev/null
@@ -1,21 +0,0 @@
-fn main() {
-    println!("{}", my_atoi(String::from("2147483648")));
-}
-
-pub fn my_atoi(s: String) -> i32 {
-    let s = s.trim();
-    let is_neg = s.starts_with('-');
-    let skip_sign = if is_neg || s.starts_with('+') { 1 } else { 0 };
-    let mut result = 0i32;
-    for byte in s.bytes().skip(skip_sign) {
-        if byte < b'0' || byte > b'9' { break; }
-        let digit = (byte - b'0') as i32;
-        if let Some(checked_result) = result.checked_mul(10).and_then(|n| n.checked_add(digit)) {
-            result = checked_result;
-        } else {
-            return if is_neg { i32::MIN } else { i32::MAX };
-        }
-    }
-    if is_neg { result = -result; }
-    return result;
-}
diff --git a/src/bin/9_palindrome_number.rs b/src/bin/9_palindrome_number.rs
deleted file mode 100644
index a5b717e..0000000
--- a/src/bin/9_palindrome_number.rs
+++ /dev/null
@@ -1,14 +0,0 @@
-fn main() {
-
-}
-
-pub fn is_palindrome(x: i32) -> bool {
-    if x < 0 { return false; }
-    let (mut x_copy, mut reversed) = (x as u32, 0u32);
-    while x_copy > 0 {
-        reversed *= 10;
-        reversed += x_copy % 10;
-        x_copy /= 10;
-    }
-    return reversed == x as u32;
-}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..4a2f141
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,16 @@
+pub mod p1_two_sum;
+pub mod p2_add_two_numbers;
+pub mod p3_longest_substring_without_repeating_characters;
+pub mod p4_median_of_two_sorted_arrays;
+pub mod p5_longest_palindrome_substring;
+pub mod p6_zigzag_conversion;
+pub mod p7_reverse_integer;
+pub mod p8_string_to_integer;
+pub mod p9_palindrome_number;
+pub mod p10_regular_expression_matching;
+pub mod p11_container_with_most_water;
+pub mod p12_integer_to_roman;
+pub mod p13_roman_to_integer;
+pub mod p14_longest_common_prefix;
+pub mod p15_3sum;
+pub mod p16_3sum_closest;
diff --git a/src/p10_regular_expression_matching.rs b/src/p10_regular_expression_matching.rs
new file mode 100644
index 0000000..15a54d7
--- /dev/null
+++ b/src/p10_regular_expression_matching.rs
@@ -0,0 +1,34 @@
+pub struct Solution;
+impl Solution {
+    pub fn is_match(s: String, p: String) -> bool {
+        let (s, p) = (s.as_bytes(), p.as_bytes());
+        let mut dp = vec![vec![false; p.len() + 1]; s.len() + 1];
+        dp[s.len()][p.len()] = true;
+        for i in (0..=s.len()).rev() {
+            for j in (0..p.len()).rev() {
+                let first_match = i < s.len() && (p[j] == b'.' || p[j] == s[i]);
+                if j + 1 < p.len() && p[j + 1] == b'*' {
+                    dp[i][j] = first_match && dp[i + 1][j] || dp[i][j + 2];
+                    continue;
+                }
+                dp[i][j] = first_match && dp[i + 1][j + 1];
+            }
+        }
+        return dp[0][0];
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::is_match("aa".to_string(), "a".to_string()), false);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::is_match("aa".to_string(), "a*".to_string()), true);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::is_match("ab".to_string(), ".*".to_string()), true);
+}
diff --git a/src/p11_container_with_most_water.rs b/src/p11_container_with_most_water.rs
new file mode 100644
index 0000000..8d0a4d8
--- /dev/null
+++ b/src/p11_container_with_most_water.rs
@@ -0,0 +1,29 @@
+pub struct Solution;
+impl Solution {
+    pub fn max_area(height: Vec<i32>) -> i32 {
+        let (mut left, mut right) = (0, height.len() - 1);
+        let mut max_water = 0;
+        while left < right {
+            let x = (right - left) as i32; let h;
+            if height[left] < height[right] {
+                h = height[left];
+                left += 1;
+            } else {
+                h = height[right];
+                right -= 1;
+            };
+            max_water = max_water.max(h * x);
+        }
+        return max_water;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::max_area(vec![1,8,6,2,5,4,8,3,7]), 49);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::max_area(vec![1,1]), 1);
+}
diff --git a/src/p12_integer_to_roman.rs b/src/p12_integer_to_roman.rs
new file mode 100644
index 0000000..2ef0a4f
--- /dev/null
+++ b/src/p12_integer_to_roman.rs
@@ -0,0 +1,49 @@
+pub struct Solution;
+impl Solution {
+    pub fn int_to_roman(num: i32) -> String {
+        let roman_nums = vec!['M', 'D', 'C', 'L', 'X', 'V', 'I'];
+        let mut result = String::with_capacity(15);
+        let (mut num, mut divisor) = (num, 1000);
+        for i in (0..roman_nums.len()).step_by(2) {
+            let roman = roman_nums[i];
+            let roman_amount = num / divisor;
+            match roman_amount {
+                0 => (),
+                1..=3 => {
+                    for _ in 0..roman_amount { result.push(roman); }
+                },
+                5..=8 => {
+                    let complement = roman_nums[i - 1];
+                    result.push(complement);
+                    for _ in 0..(roman_amount-5) { result.push(roman); }
+                },
+                4 | 9 => {
+                    let complement_index = i - roman_amount as usize / 4; 
+                    let complement = roman_nums[complement_index];
+                    result.push(roman);
+                    result.push(complement);
+                },
+                _ => ()
+            }
+            num %= divisor;
+            divisor /= 10;
+        }
+        if result.is_empty() { result.push('0'); }
+        return result;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::int_to_roman(3), "III".to_string());
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::int_to_roman(58), "LVIII".to_string());
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::int_to_roman(1994), "MCMXCIV".to_string());
+}
diff --git a/src/p13_roman_to_integer.rs b/src/p13_roman_to_integer.rs
new file mode 100644
index 0000000..2553427
--- /dev/null
+++ b/src/p13_roman_to_integer.rs
@@ -0,0 +1,27 @@
+pub struct Solution;
+impl Solution {
+    pub fn roman_to_int(s: String) -> i32 {
+        s.chars().fold(0, |acc, c| {
+            let num = match c {
+                'M' => 1000, 'D' => 500, 'C' => 100, 'L' => 50,
+                'X' => 10, 'V' => 5, 'I' => 1, _ => 0
+            };
+            acc + num - 2 * (acc % num)
+        })
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::roman_to_int("III".to_string()), 3);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::roman_to_int("LVIII".to_string()), 58);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::roman_to_int("MCMXCIV".to_string()), 1994);
+}
diff --git a/src/p14_longest_common_prefix.rs b/src/p14_longest_common_prefix.rs
new file mode 100644
index 0000000..e2f3147
--- /dev/null
+++ b/src/p14_longest_common_prefix.rs
@@ -0,0 +1,30 @@
+pub struct Solution;
+impl Solution {
+    pub fn longest_common_prefix(strs: Vec<String>) -> String {
+        let mut result = String::with_capacity(200);
+        let first_str = strs[0].as_bytes();
+        if first_str.is_empty() { return result; }
+        for i in 0..first_str.len() {
+            let c = first_str[i];
+            for j in 1..strs.len() {
+                if i >= strs[j].len() || c != strs[j].as_bytes()[i] {
+                    return result;
+                }
+            }
+            result.push(c as char);
+        }
+        return result;
+    }
+}
+
+#[test]
+fn test1() {
+    let strs = vec!["flower".to_string(),"flow".to_string(),"flight".to_string()];
+    assert_eq!(Solution::longest_common_prefix(strs), "fl".to_string());
+}
+
+#[test]
+fn test2() {
+    let strs = vec!["dog".to_string(),"racecar".to_string(),"car".to_string()];
+    assert_eq!(Solution::longest_common_prefix(strs), "".to_string());
+}
diff --git a/src/p15_3sum.rs b/src/p15_3sum.rs
new file mode 100644
index 0000000..8858ff4
--- /dev/null
+++ b/src/p15_3sum.rs
@@ -0,0 +1,43 @@
+pub struct Solution;
+impl Solution {
+    pub fn three_sum(mut nums: Vec<i32>) -> Vec<Vec<i32>> {
+        let mut result = Vec::<Vec<i32>>::new();
+        nums.sort();
+        for i in 0..nums.len()-2 {
+            if i > 0 && nums[i] == nums[i - 1] { continue; }
+            let (mut j, mut k) = (i + 1, nums.len() - 1);
+            while j < k {
+                if j > i + 1 && nums[j - 1] == nums[j] {
+                    j += 1; continue;
+                }
+                if k < nums.len() - 1 && nums[k + 1] == nums[k] {
+                    k -= 1; continue;
+                }
+                match (nums[i] + nums[j] + nums[k]).cmp(&0) {
+                    std::cmp::Ordering::Less => { j += 1; },
+                    std::cmp::Ordering::Greater => { k -= 1 },
+                    std::cmp::Ordering::Equal => {
+                        result.push(vec![nums[i], nums[j], nums[k]]);
+                        j += 1; k -= 1;
+                    }
+                }
+            }
+        }
+        return result;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::three_sum(vec![-1,0,1,2,-1,-4]), vec![vec![-1,-1,2], vec![-1,0,1]]);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::three_sum(vec![0,1,1]), Vec::<Vec<i32>>::new());
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::three_sum(vec![0,0,0]), vec![vec![0,0,0]]);
+}
\ No newline at end of file
diff --git a/src/p16_3sum_closest.rs b/src/p16_3sum_closest.rs
new file mode 100644
index 0000000..c16a072
--- /dev/null
+++ b/src/p16_3sum_closest.rs
@@ -0,0 +1,17 @@
+pub struct Solution;
+impl Solution {
+    pub fn three_sum_closest(nums: Vec<i32>, target: i32) -> i32 {
+        
+        return 0;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::three_sum_closest(vec![-1,2,1,-4], 1), 2);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::three_sum_closest(vec![0,0,0], 1), 0);
+}
diff --git a/src/p1_two_sum.rs b/src/p1_two_sum.rs
new file mode 100644
index 0000000..2b3d484
--- /dev/null
+++ b/src/p1_two_sum.rs
@@ -0,0 +1,35 @@
+use std::collections::HashMap;
+
+pub struct Solution;
+impl Solution {
+    pub fn two_sum(nums: Vec<i32>, target: i32) -> Vec<i32> {
+        let mut components: HashMap<i32, usize> = HashMap::new();
+        for i in 0..nums.len() {
+            let component = target - nums[i];
+            if let Some(j) = components.get(&component) {
+                return vec![i as i32, *j as i32];
+            }
+            components.insert(nums[i], i);
+        }
+        return Vec::new();
+    }
+}
+
+#[test]
+fn test1() {
+    let actual = Solution::two_sum(vec![2,7,11,15], 9);
+    assert!(actual == vec![1,0] || actual == vec![0,1]);
+}
+
+#[test]
+fn test2() {
+    let actual = Solution::two_sum(vec![3,2,4], 6);
+    assert!(actual == vec![1,2] || actual == vec![2,1]);
+}
+
+#[test]
+fn test3() {
+    let actual = Solution::two_sum(vec![3,3], 6);
+    assert!(actual == vec![1,0] || actual == vec![0,1]);
+}
+    
\ No newline at end of file
diff --git a/src/p2_add_two_numbers.rs b/src/p2_add_two_numbers.rs
new file mode 100644
index 0000000..25b80c3
--- /dev/null
+++ b/src/p2_add_two_numbers.rs
@@ -0,0 +1,50 @@
+pub struct Solution;
+impl Solution {
+    pub fn add_two_numbers(l1: Option<Box<ListNode>>, l2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
+        let (mut l1, mut l2) = (l1, l2);
+        let mut head = Box::new(ListNode::new(0));
+        let mut tail = &mut head;
+        loop {
+            let mut sum = tail.val;
+            if let Some(node) = &l1 {
+                sum += node.val;
+                l1 = node.next.clone();
+            }
+            if let Some(node) = &l2 {
+                sum += node.val;
+                l2 = node.next.clone();
+            }
+            let next_node = Box::new(ListNode::new(sum / 10));
+            tail.val = sum % 10;
+            if l1.is_none() && l2.is_none() {
+                if next_node.val > 0 { tail.next = Some(next_node); }
+                break;
+            }
+            tail.next = Some(next_node);
+            tail = tail.next.as_mut().unwrap();
+        }
+        return Some(head);
+    }    
+}
+
+// Definition for singly-linked list.
+#[derive(PartialEq, Eq, Clone, Debug)]
+pub struct ListNode {
+    pub val: i32,
+    pub next: Option<Box<ListNode>>
+}
+
+impl ListNode {
+    #[inline]
+    fn new(val: i32) -> Self {
+        ListNode {
+            next: None,
+            val
+        }
+    }
+}
+
+#[test]
+fn test() {
+    
+}
diff --git a/src/p3_longest_substring_without_repeating_characters.rs b/src/p3_longest_substring_without_repeating_characters.rs
new file mode 100644
index 0000000..3c48887
--- /dev/null
+++ b/src/p3_longest_substring_without_repeating_characters.rs
@@ -0,0 +1,34 @@
+use std::collections::HashMap;
+
+pub struct Solution;
+impl Solution {
+    pub fn length_of_longest_substring(s: String) -> i32 {
+        let mut seen: HashMap<char, usize> = HashMap::with_capacity(80);
+        let (mut start_index, mut max_length) = (0usize, 0usize);
+        for (i, c) in s.chars().enumerate() {
+            if let Some(index) = seen.get(&c) {
+                max_length = max_length.max(i - start_index);
+                start_index = *index + 1;
+                seen.retain(|_, i| *i >= start_index);
+            }
+            seen.insert(c, i);
+        }
+        max_length = max_length.max(s.len() - start_index);
+        return max_length as i32;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::length_of_longest_substring("abcabcbb".to_string()), 3);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::length_of_longest_substring("bbbbb".to_string()), 1);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::length_of_longest_substring("pwwkew".to_string()), 3);
+}
diff --git a/src/p4_median_of_two_sorted_arrays.rs b/src/p4_median_of_two_sorted_arrays.rs
new file mode 100644
index 0000000..4a7189f
--- /dev/null
+++ b/src/p4_median_of_two_sorted_arrays.rs
@@ -0,0 +1,31 @@
+pub struct Solution;
+impl Solution {
+    // TODO: reduce algorithm complexity from O(m+n) to O(log(m+n))
+    pub fn find_median_sorted_arrays(nums1: Vec<i32>, nums2: Vec<i32>) -> f64 {
+        let length = nums1.len() + nums2.len();
+        let mut nums3 = vec![0i32; length];
+        let (mut m, mut n) = (0usize, 0usize);
+        while m + n < length {
+            let x1 = if m < nums1.len() { nums1[m] } else { i32::MAX };
+            let x2 = if n < nums2.len() { nums2[n] } else { i32::MAX };
+            if x1 <= x2 {
+                nums3[m + n] = x1;
+                m += 1;
+            } else {
+                nums3[m + n] = x2;
+                n += 1;
+            }
+        }
+        return (nums3[(length - 1) / 2] + nums3[length / 2]) as f64 / 2.0;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::find_median_sorted_arrays(vec![1,3], vec![2]), 2.0);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::find_median_sorted_arrays(vec![1,2], vec![3,4]), 2.5);
+}
diff --git a/src/p5_longest_palindrome_substring.rs b/src/p5_longest_palindrome_substring.rs
new file mode 100644
index 0000000..04a7342
--- /dev/null
+++ b/src/p5_longest_palindrome_substring.rs
@@ -0,0 +1,27 @@
+pub struct Solution;
+impl Solution {
+    pub fn longest_palindrome(s: String) -> String {
+        let mut max_indexes = (0usize, 1usize);
+        for i in 0..(s.len()-1)*2 {
+            let (mut start, mut end) = (i / 2 + i % 2, i / 2);
+            while start > 0 && end < s.len() - 1 {
+                if s.as_bytes()[start - 1] != s.as_bytes()[end + 1] { break; }
+                start -= 1; end += 1;
+            }
+            let length = end + 1 - start;
+            if length > max_indexes.1 - max_indexes.0 { max_indexes = (start, end + 1); }
+        }
+        return String::from(&s[max_indexes.0..max_indexes.1]);
+    }
+}
+
+#[test]
+fn test1() {
+    let actual = Solution::longest_palindrome("babad".to_string());
+    assert!(actual == "bab".to_string() || actual == "aba".to_string());
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::longest_palindrome("cbbd".to_string()), "bb".to_string());
+}
diff --git a/src/p6_zigzag_conversion.rs b/src/p6_zigzag_conversion.rs
new file mode 100644
index 0000000..1946c6e
--- /dev/null
+++ b/src/p6_zigzag_conversion.rs
@@ -0,0 +1,34 @@
+pub struct Solution;
+impl Solution {
+    pub fn convert(s: String, num_rows: i32) -> String {
+        if num_rows <= 1 { return s; }
+        let mut result = String::with_capacity(s.len());
+        let num_rows = num_rows as usize;
+        for i in 0..num_rows {
+            for j in (i..s.len()).step_by(num_rows * 2 - 2) {
+                result.push(s.as_bytes()[j] as char);
+                if i > 0 && i < num_rows - 1 {
+                    let diagonal_index = j + 2 * (num_rows - i - 1);
+                    if diagonal_index >= s.len() { continue; }
+                    result.push(s.as_bytes()[diagonal_index] as char);
+                }
+            }
+        }
+        return result;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 3), "PAHNAPLSIIGYIR".to_string());
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::convert("PAYPALISHIRING".to_string(), 4), "PINALSIGYAHRPI".to_string());
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::convert("A".to_string(), 1), "A".to_string());
+}
diff --git a/src/p7_reverse_integer.rs b/src/p7_reverse_integer.rs
new file mode 100644
index 0000000..e4d752b
--- /dev/null
+++ b/src/p7_reverse_integer.rs
@@ -0,0 +1,33 @@
+pub struct Solution;
+impl Solution {
+    // problem doesn't allow using 64-bit numbers
+    pub fn reverse(x: i32) -> i32 {
+        let is_negative = x < 0;
+        let (mut x, mut result) = (x.checked_abs().unwrap_or(0), 0i32);
+        while x > 9 {
+            result *= 10;
+            result += x % 10;
+            x /= 10;
+        }
+        return result.checked_mul(10).and_then(|mut n| {
+            n += x % 10;
+            if is_negative { n = -n; }
+            Some(n)
+        }).unwrap_or(0);
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::reverse(123), 321);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::reverse(-123), -321);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::reverse(120), 21);
+}
diff --git a/src/p8_string_to_integer.rs b/src/p8_string_to_integer.rs
new file mode 100644
index 0000000..9b0f433
--- /dev/null
+++ b/src/p8_string_to_integer.rs
@@ -0,0 +1,35 @@
+pub struct Solution;
+impl Solution {
+    pub fn my_atoi(s: String) -> i32 {
+        let s = s.trim();
+        let is_neg = s.starts_with('-');
+        let skip_sign = if is_neg || s.starts_with('+') { 1 } else { 0 };
+        let mut result = 0i32;
+        for byte in s.bytes().skip(skip_sign) {
+            if byte < b'0' || byte > b'9' { break; }
+            let digit = (byte - b'0') as i32;
+            if let Some(checked_result) = result.checked_mul(10).and_then(|n| n.checked_add(digit)) {
+                result = checked_result;
+            } else {
+                return if is_neg { i32::MIN } else { i32::MAX };
+            }
+        }
+        if is_neg { result = -result; }
+        return result;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::my_atoi("42".to_string()), 42);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::my_atoi("   -42".to_string()), -42);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::my_atoi("4193 with words".to_string()), 4193);
+}
diff --git a/src/p9_palindrome_number.rs b/src/p9_palindrome_number.rs
new file mode 100644
index 0000000..b95e9ca
--- /dev/null
+++ b/src/p9_palindrome_number.rs
@@ -0,0 +1,28 @@
+pub struct Solution;
+impl Solution {
+    pub fn is_palindrome(x: i32) -> bool {
+        if x < 0 { return false; }
+        let (mut x_copy, mut reversed) = (x as u32, 0u32);
+        while x_copy > 0 {
+            reversed *= 10;
+            reversed += x_copy % 10;
+            x_copy /= 10;
+        }
+        return reversed == x as u32;
+    }
+}
+
+#[test]
+fn test1() {
+    assert_eq!(Solution::is_palindrome(121), true);
+}
+
+#[test]
+fn test2() {
+    assert_eq!(Solution::is_palindrome(-121), false);
+}
+
+#[test]
+fn test3() {
+    assert_eq!(Solution::is_palindrome(10), false);
+}