solve: Week 02 3 sum

Author: eunice-hong

3sum/eunice-hong.ts

@@ -0,0 +1,36 @@
+function threeSum(nums: number[]): number[][] {
+  // Sort the array to make it easier to find triplets that sum to zero
+  nums.sort((a, b) => a - b);
+  const result: number[][] = [];
+
+  // Iterate through the array to find triplets that sum to zero
+  for (let i = 0; i < nums.length - 2; i++) {
+    // Skip duplicates
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+
+    // Use two pointers to find the other two numbers
+    let left = i + 1;
+    let right = nums.length - 1;
+
+    while (left < right) {
+      const sum = nums[i] + nums[left] + nums[right];
+      if (sum === 0) {
+        // Add the triplet to the result array
+        result.push([nums[i], nums[left], nums[right]]);
+        left++;
+        right--;
+        // Skip duplicates
+        while (left < right && nums[left] === nums[left - 1]) left++;
+        while (left < right && nums[right] === nums[right + 1]) right--;
+      } else if (sum < 0) {
+        // Move the left pointer to the right to increase the sum
+        left++;
+      } else {
+        // Move the right pointer to the left to decrease the sum
+        right--;
+      }
+    }
+  }
+
+  return result;
+}