15. 3Sum

Author: Kohei Asai

solutions/3sum.ts

@@ -0,0 +1,53 @@
+// 15. 3Sum
+// https://leetcode.com/problems/3sum/
+export default function threeSum(nums: number[]): number[][] {
+  const triplets: [number, number, number][] = [];
+
+  nums.sort((a, b) => a - b);
+
+  for (let i = 0; i < nums.length - 2; ++i) {
+    if (nums[i] > 0) break;
+    if (nums[i] === nums[i - 1]) continue;
+
+    let left = i + 1;
+    let right = nums.length - 1;
+    let target = -nums[i];
+
+    while (left < right) {
+      if (nums[left] + nums[right] < target) {
+        while (nums[left + 1] === nums[left]) {
+          left += 1;
+        }
+
+        left += 1;
+
+        continue;
+      }
+
+      if (nums[left] + nums[right] > target) {
+        while (nums[right - 1] === nums[right]) {
+          right -= 1;
+        }
+
+        right -= 1;
+
+        continue;
+      }
+
+      triplets.push([nums[i], nums[left], nums[right]]);
+
+      while (nums[left + 1] === nums[left]) {
+        left += 1;
+      }
+
+      while (nums[right - 1] === nums[right]) {
+        right -= 1;
+      }
+
+      left += 1;
+      right -= 1;
+    }
+  }
+
+  return triplets;
+}