feat: implement threeSum algorithm

- Finds triplets in unsorted array that add up to 0.

Author: francislagares

.vscode/launch.json

@@ -5,13 +5,44 @@
       "type": "node",
       "request": "launch",
       "name": "Vitest Current File",
-      "program": "${workspaceFolder}/node_modules/.bin/vitest",
-      "args": ["${fileBasenameNoExtension}", "--config", "vite.config.ts"],
+      "runtimeExecutable": "pnpm",
+      "runtimeArgs": [
+        "exec",
+        "vitest",
+        "${fileBasenameNoExtension}",
+        "--config",
+        "vite.config.mts"
+      ],
+      "console": "integratedTerminal",
+      "internalConsoleOptions": "neverOpen"
+    },
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "Debug TypeScript Current File",
+      "runtimeArgs": ["-r", "tsx"],
+      "args": ["${relativeFile}"],
+      "cwd": "${workspaceRoot}",
+      "console": "integratedTerminal",
+      "internalConsoleOptions": "neverOpen"
+    },
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "Debug TypeScript with pnpm",
+      "runtimeExecutable": "pnpm",
+      "runtimeArgs": ["run", "debug"],
       "console": "integratedTerminal",
       "internalConsoleOptions": "neverOpen",
-      "windows": {
-        "program": "${workspaceFolder}/node_modules/jest/bin/jest"
-      }
+      "skipFiles": ["<node_internals>/**"]
+    },
+    {
+      "type": "node",
+      "request": "attach",
+      "name": "Attach to Process",
+      "port": 9229,
+      "restart": true,
+      "skipFiles": ["<node_internals>/**"]
     }
   ]
 }

package.json

@@ -9,8 +9,9 @@
   "scripts": {
     "build-ts": "tsc",
     "build-dev": "tsc --watch",
-    "start": "nodemon dist/index.js",
+    "start": "ts-node src/index.ts",
     "dev": "concurrently \"pnpm:build-dev\" \"pnpm:start\"",
+    "debug": "node --inspect-brk -r ts-node/register src/index.ts",
     "test:ci": "vitest run",
     "test:watch": "vitest watch --ui",
     "test:coverage": "vitest run --coverage",
@@ -42,6 +43,8 @@
     "lint-staged": "^15.3.0",
     "nodemon": "^3.0.1",
     "prettier": "^3.0.3",
+    "ts-node": "^10.9.2",
+    "tsx": "^4.19.2",
     "typescript": "^5.2.2",
     "vite-tsconfig-paths": "^5.1.4",
     "vitest": "^2.1.8",

pnpm-lock.yaml

@@ -0,0 +1,47 @@
+import { threeSum } from '../three-sum';
+
+describe('ThreeSum', () => {
+  test('should return empty array when input array is empty', () => {
+    expect(threeSum([])).toEqual([]);
+  });
+
+  test('should return empty array when no triplets sum to zero', () => {
+    expect(threeSum([1, 2, 3, 4, 5])).toEqual([]);
+  });
+
+  test('should find single triplet that sums to zero', () => {
+    expect(threeSum([-1, 0, 1])).toEqual([[-1, 0, 1]]);
+  });
+
+  test('should find multiple triplets that sum to zero', () => {
+    const nums = [-1, 0, 1, 2, -1, -4];
+    const result = threeSum(nums);
+
+    // Each triplet should be sorted internally
+    const expected = [
+      [-1, 0, 1], // First solution
+      [-1, -1, 2], // Second solution
+    ];
+
+    // Verify solutions exist
+    expected.forEach(triplet => {
+      expect(result).toContainEqual(triplet);
+    });
+
+    // Verify count matches
+    expect(result.length).toBe(expected.length);
+  });
+
+  test('should handle duplicate numbers correctly', () => {
+    const result = threeSum([-2, 0, 0, 2, 2]);
+    expect(result).toEqual([[-2, 0, 2]]);
+  });
+
+  test('should handle all negative numbers', () => {
+    expect(threeSum([-1, -2, -3, -4])).toEqual([]);
+  });
+
+  test('should handle array with all zeros', () => {
+    expect(threeSum([0, 0, 0])).toEqual([[0, 0, 0]]);
+  });
+});

src/algorithms/three-sum/tests/three-sum.test.ts

@@ -0,0 +1,38 @@
+export const threeSum = (nums: number[]) => {
+  nums.sort((a, b) => a - b); // Sort the array
+  const triplets = [];
+
+  for (let i = 0; i < nums.length - 2; i++) {
+    // Skip the duplicate elements for the first number
+    if (i > 0 && nums[i] === nums[i - 1]) continue;
+
+    let left = i + 1;
+    let right = nums.length - 1;
+
+    while (left < right) {
+      const sum = nums[i] + nums[left] + nums[right];
+
+      if (sum === 0) {
+        triplets.push([nums[i], nums[left], nums[right]]);
+
+        // Skip the duplicate elements for the second and third numbers
+        while (left < right && nums[left] === nums[left + 1]) left++;
+        while (left < right && nums[right] === nums[right - 1]) right--;
+
+        left++;
+        right--;
+      } else if (sum < 0) {
+        left++;
+      } else {
+        right--;
+      }
+    }
+  }
+
+  return triplets;
+};
+
+const nums = [-3, 0, 1, 2, -1, 1, -2];
+const triplets = threeSum(nums);
+
+console.log(triplets);