feat: add Combination Sum II

Author: dukeluo

README.md

@@ -75,6 +75,7 @@ Roadmap: https://neetcode.io/roadmap
 | 78   | [Subsets](https://leetcode.com/problems/subsets/description/)                                                                                                     | Medium     | [ts](./TypeScript/78.subsets.ts)                                                              | Backtracking     |
 | 39   | [Combination Sum](https://leetcode.com/problems/combination-sum/description/)                                                                                     | Medium     | [ts](./TypeScript/39.combination-sum.ts)                                                      | Backtracking     |
 | 90   | [Subsets II](https://leetcode.com/problems/subsets-ii/description/)                                                                                               | Medium     | [ts](./TypeScript/90.subsets-ii.ts)                                                           | Backtracking     |
+| 40   | [Combination Sum II](https://leetcode.com/problems/combination-sum-ii/description/)                                                                               | Medium     | [ts](./TypeScript/40.combination-sum-ii.ts)                                                   | Backtracking     |
 
 ### Others
 

TypeScript/40.combination-sum-ii.ts

@@ -0,0 +1,33 @@
+function combinationSum2(candidates: number[], target: number): number[][] {
+  const combinations: number[][] = [];
+
+  function backtrace(index: number, combination: number[], target: number) {
+    if (target === 0) {
+      combinations.push(combination.slice());
+      return;
+    }
+
+    if (target < 0) {
+      return;
+    }
+
+    let prev = -1;
+    for (let i = index; i < candidates.length; i++) {
+      if (candidates[i] === prev) {
+        continue;
+      }
+
+      combination.push(candidates[i]);
+      backtrace(i + 1, combination, target - candidates[i]);
+      prev = candidates[i];
+      combination.pop();
+    }
+  }
+
+  candidates.sort();
+  backtrace(0, [], target);
+
+  return combinations;
+}
+
+console.log(combinationSum2([10, 1, 2, 7, 6, 1, 5], 8));