feat: 15. 3Sum

Author: gwbaik9717

3sum/gwbaik9717.js

@@ -0,0 +1,38 @@
+// Time complexity: O(n^2)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var threeSum = function (nums) {
+  const sumsDict = new Set();
+  const sortedNums = nums.toSorted((a, b) => a - b);
+
+  const n = nums.length;
+
+  for (let i = 0; i < n - 2; i++) {
+    let left = i + 1;
+    let right = n - 1;
+    const fixed = sortedNums[i];
+
+    const targetSum = 0 - fixed;
+
+    while (left < right) {
+      const currentSum = sortedNums[left] + sortedNums[right];
+
+      if (currentSum < targetSum) {
+        left++;
+      } else if (currentSum > targetSum) {
+        right--;
+      } else {
+        const key = [fixed, sortedNums[left], sortedNums[right]];
+        sumsDict.add(key.join(","));
+        left++;
+        right--;
+      }
+    }
+  }
+
+  return Array.from(sumsDict).map((nums) => nums.split(",").map(Number));
+};