Problem 15 prototype implementation

src/bin/15_3sum.rs

@@ -1,8 +1,26 @@
 fn main() {
-
+    println!("{:?}", three_sum(vec![-1,0,1,2,-1,-4]));
 }
 
-pub fn three_sum(nums: Vec<i32>) -> Vec<Vec<i32>> {
-    
-    return vec![];
+// TODO: fix and optimize
+pub fn three_sum(mut nums: Vec<i32>) -> Vec<Vec<i32>> {
+    let mut result: Vec<Vec<i32>> = Vec::new();
+    let mut seen = std::collections::HashSet::<i32>::with_capacity(nums.len());
+    let mut seen2 = std::collections::HashSet::<i32>::with_capacity(nums.len()-1);
+    nums.sort();
+    for i in 0..nums.len()-2 {
+        if seen.contains(&nums[i]) { continue; }
+        for j in i+1..nums.len()-1 {
+            if seen2.contains(&nums[j]) { continue; }
+            for k in j+1..nums.len() {
+                if nums[i] + nums[j] + nums[k] == 0 {
+                    result.push(vec![nums[i], nums[j], nums[k]]);
+                }
+            }
+            seen2.insert(nums[j]);
+        }
+        seen.insert(nums[i]);
+        seen2.clear();
+    }
+    return result;
 }