3sum solution

Author: togo26

3sum/togo26.js

@@ -0,0 +1,57 @@
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+/// TC: TLE / SC: O(n)
+// var threeSum = function(nums) {
+//     const result = [];
+//     const memo = {};
+
+//     for (let i = 0; i < nums.length; i++) {
+//         for (let j = 0; j < nums.length; j++) {
+//             for (let k = 0; k < nums.length; k++) {
+//                 if (i === k || i === j || j === k) continue;
+//                 const comb = [nums[i], nums[j], nums[k]].sort((a, b) => a - b).join(",");
+
+//                 if (memo[comb]) continue;
+//                 if (!memo[comb]) memo[comb] = true;
+//                 const sum = nums[i] + nums[j] + nums[k];
+//                 if (sum === 0) result.push([nums[i], nums[j], nums[k]]);
+//             }
+//         }
+//     }
+
+//     return result;
+// };
+
+// TC: O(n^2) / SC: O(1)
+var threeSum = function (nums) {
+  const result = [];
+
+  nums.sort((a, b) => a - b);
+
+  for (let i = 0; i < nums.length; i++) {
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+    if (nums[i] > 0) break;
+
+    let left = i + 1;
+    let right = nums.length - 1;
+
+    while (left < right) {
+      const sum = nums[left] + nums[right];
+      if (sum === -nums[i]) {
+        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 < -nums[i]) {
+        left++;
+      } else {
+        right--;
+      }
+    }
+  }
+
+  return result;
+};