Feat: 15. 3Sum

Author: HC-kang

3sum/HC-kang.ts

@@ -0,0 +1,36 @@
+/**
+ * https://leetcode.com/problems/3sum/description
+ * T.C: O(n^2)
+ * S.C: O(1)
+ */
+function threeSum(nums: number[]): number[][] {
+  nums.sort((a, b) => a - b);
+
+  const result: number[][] = [];
+
+  for (let i = 0; i < nums.length - 2; i++) { // O(n)
+    if (i > 0 && nums[i] == nums[i - 1]) continue;
+
+    let left = i + 1;
+    let right = nums.length - 1;
+
+    while (left < right) { // O(n)
+      const sum = nums[i] + nums[left] + nums[right];
+      if (sum == 0) {
+        result.push([nums[i], nums[left], nums[right]]);
+
+        while (left < right && nums[left] == nums[left + 1]) left++;
+        while (left < right && nums[right] == nums[right - 1]) right--;
+
+        left++;
+        right--;
+      } else if (sum < 0) {
+        left++;
+      } else {
+        right--;
+      }
+    }
+  }
+
+  return result;
+}