Implemented problems 4-9

.vscode/settings.json

@@ -1,5 +1,6 @@
 {
     "rust-analyzer.linkedProjects": [
         "./Cargo.toml"
-    ]
+    ],
+    "codetogether.virtualCursorJoin": "sharedVirtualCursor"
 }

src/bin/1_two_sum.rs

@@ -8,8 +8,9 @@ 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];
-        let j = components.get(&component);
-        if j.is_some() { return vec![i as i32, *j.unwrap() as i32]; }
+        if let Some(j) = components.get(&component) {
+            return vec![i as i32, *j as i32];
+        }
         components.insert(nums[i], i);
     }
     return Vec::new();

src/bin/2_add_two_numbers.rs

@@ -2,6 +2,7 @@ fn main() {
 
 }
 
+// TODO: implement algorithm
 pub fn add_two_numbers(l1: Option<Box<ListNode>>, l2: Option<Box<ListNode>>) -> Option<Box<ListNode>> {
     return None;
 }

src/bin/4_median_of_two_sorted_arrays.rs

@@ -2,7 +2,23 @@ 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 {
-    
-    return 0.0;
+    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;
+        }
+    }
+    let mut result = nums3[length / 2] as f64;
+    if length % 2 == 0 { result = (result + nums3[length / 2 - 1] as f64) / 2.0; }
+    return result;
 }

src/bin/5_longest_palindrome_substring.rs

@@ -0,0 +1,21 @@
+fn main() {
+    println!("{}", longest_palindrome(String::from("bccd")));
+}
+
+pub fn longest_palindrome(s: String) -> String {
+    if s.len() <= 1 { return s; }
+    let mut longest_palindrome = String::from(&s[0..1]);
+    for i in 0..s.len()-1 {
+        for even_palindrome_offset in 0..=1 {
+            let (mut start, mut end) = (i + even_palindrome_offset, i);
+            while start > 0 && end < s.len() - 1 {
+                if s.as_bytes()[start - 1] != s.as_bytes()[end + 1] { break; }
+                start -= 1; end += 1;
+            }
+            if end + 1 - start > longest_palindrome.len() {
+                longest_palindrome = String::from(&s[start..end+1]);
+            }
+        }
+    }
+    return longest_palindrome;
+}

src/bin/6_zigzag_conversion.rs

@@ -0,0 +1,20 @@
+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;
+}

src/bin/7_reverse_integer.rs

@@ -0,0 +1,19 @@
+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);
+}

src/bin/8_string_to_integer.rs

@@ -0,0 +1,21 @@
+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;
+}

src/bin/9_palindrome_number.rs

@@ -0,0 +1,14 @@
+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;
+}