3sum solution

3sum/yoonthecoder.js

@@ -0,0 +1,27 @@
+var threeSum = function (nums) {
+  nums.sort((a, b) => a - b);
+  const results = [];
+  for (let i = 0; i < nums.length - 2; i++) {
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+    let left = i + 1;
+    let right = nums.length - 1;
+    while (left < right) {
+      const currSum = nums[i] + nums[left] + nums[right];
+
+      if (currSum == 0) {
+        results.push([nums[i], nums[left], nums[right]]);
+        left++;
+        right--;
+        // to avoid duplicates
+        while (left < right && nums[left] === nums[left - 1]) left++;
+        while (left < right && nums[right] === nums[right + 1]) right--;
+      } else if (currSum < 0) {
+        left++;
+      } else right--;
+    }
+  }
+  return results;
+};
+
+// Time complexity: O(n^2);
+// Space complexity: O(n)