Feat | NeetCode | Roadmap | 3Sum

README.md

@@ -81,4 +81,5 @@
   - [Task #9](src/neetcode/arrays-&-hashing/longest-consecutive-sequence) - _Longest Consecutive Sequence_ - _[check the task](https://neetcode.io/problems/longest-consecutive-sequence)_
 - Two Pointers
   - [Task #10](src/neetcode/two-pointers/valid-palindrome) - _Valid Palindrome_ - _[check the task](https://neetcode.io/problems/is-palindrome)_
-  - [Task #11](src/neetcode/two-pointers/two-sum-ii-input-array-is-sorted) - _Two Sum II Input Array Is Sorted_ - _[check the task](https://neetcode.io/problems/two-integer-sum-ii)_
+  - [Task #11](src/neetcode/two-pointers/two-sum-ii-input-array-is-sorted) - _Two Sum II Input Array Is Sorted_ - _[check the task](https://neetcode.io/problems/two-integer-sum-ii)_
+  - [Task #12](src/neetcode/two-pointers/3sum) - _3Sum_ - _[check the task](https://neetcode.io/problems/three-integer-sum)_

src/neetcode/two-pointers/3sum/solution.test.ts

@@ -0,0 +1,27 @@
+import { threeSum } from './solution';
+
+describe('3Sum | NeetCode | RoadMap | Testcases', () => {
+  test('#1 Some triplets', () => {
+    const nums = [-1, 0, 1, 2, -1, -4];
+    const expected = [
+      [-1, -1, 2],
+      [-1, 0, 1],
+    ];
+    const output = threeSum(nums);
+    expect(output).toEqual(expected);
+  });
+
+  test('#2 No triplets', () => {
+    const nums = [0, 1, 1];
+    const expected: number[][] = [];
+    const output = threeSum(nums);
+    expect(output).toEqual(expected);
+  });
+
+  test('#3 One triplet', () => {
+    const nums = [0, 0, 0];
+    const expected: number[][] = [[0, 0, 0]];
+    const output = threeSum(nums);
+    expect(output).toEqual(expected);
+  });
+});

src/neetcode/two-pointers/3sum/solution.ts

@@ -0,0 +1,38 @@
+/**
+ * @param {number[]} nums - an integer array
+ * @return {number[][]} - all the triplets `[nums[i], nums[j], nums[k]]` where `nums[i] + nums[j] + nums[k] == 0`,
+ * and the indices `i, j, k` are all distinct.
+ */
+export const threeSum = (nums: number[]): number[][] => {
+  const res: number[][] = [];
+  nums.sort((a, b) => a - b);
+
+  for (let i = 0; i < nums.length; i++) {
+    if (nums[i] > 0) {
+      break;
+    }
+    if (i > 0 && nums[i] === nums[i - 1]) {
+      continue;
+    }
+
+    let l = i + 1;
+    let r = nums.length - 1;
+
+    while (l < r) {
+      const sum = nums[i] + nums[l] + nums[r];
+      if (sum > 0) {
+        r--;
+      } else if (sum < 0) {
+        l++;
+      } else {
+        res.push([nums[i], nums[l], nums[r]]);
+        l++;
+        r--;
+        while (l < r && nums[l] === nums[l - 1]) {
+          l++;
+        }
+      }
+    }
+  }
+  return res;
+};