40. 组合总和 II

Author: w2xi

README.md

@@ -32,6 +32,7 @@
 |34|[在排序数组中查找元素的第一个和最后一个位置](https://leetcode.cn/problems/find-first-and-last-position-of-element-in-sorted-array/)|[JavaScript](./algorithms/find-first-and-last-position-of-element-in-sorted-array.js)|Medium|
 |35|[搜索插入位置](https://leetcode.cn/problems/search-insert-position/)|[JavaScript](./algorithms/search-insert-position.js)|Easy|
 |39|[组合总和](https://leetcode.cn/problems/combination-sum/)|[JavaScript](./algorithms/combination-sum.js)|Medium|
+|40|[组合总和 II](https://leetcode.cn/problems/combination-sum-ii/)|[JavaScript](./algorithms/combination-sum-ii.js)|Medium|
 |48|[旋转图像](https://leetcode.cn/problems/rotate-image/)|[JavaScript](./algorithms/rotate-image.js)|Medium|
 |49|[字母异位词分组](https://leetcode.cn/problems/group-anagrams/)|[JavaScript](./algorithms/group-anagrams.js)|Medium|
 |54|[螺旋矩阵](https://leetcode.cn/problems/spiral-matrix/)|[JavaScript](./algorithms/spiral-matrix.js)|Medium|

algorithms/combination-sum-ii.js

@@ -0,0 +1,41 @@
+/**
+ * 40. 组合总和 II
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum2 = function (candidates, target) {
+  candidates.sort((a, b) => a - b);
+
+  const result = [];
+  const path = [];
+  let sum = 0;
+
+  // [1,1,2,5,6,7,10]
+
+  const backtracking = (candidates, target, startIndex) => {
+    if (sum === target) {
+      result.push(path.slice());
+      return;
+    }
+    for (
+      let i = startIndex;
+      i < candidates.length && sum + candidates[i] <= target; // 剪枝
+      i++
+    ) {
+      // 要对同一树层使用过的元素进行跳过
+      if (i > startIndex && candidates[i] === candidates[i - 1]) {
+        continue;
+      }
+      const curr = candidates[i];
+      path.push(curr);
+      sum += curr;
+      backtracking(candidates, target, i + 1);
+      sum -= curr;
+      path.pop();
+    }
+  };
+  backtracking(candidates, target, 0);
+
+  return result;
+};