39. 组合总和

Author: w2xi

README.md

@@ -31,6 +31,7 @@
 |28|[实现 strStr()](https://leetcode-cn.com/problems/implement-strstr/)|[JavaScript](./algorithms/implement-strstr.js)|Easy|
 |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|
 |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.js

@@ -0,0 +1,30 @@
+/**
+ * 39. 组合总和
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function (candidates, target) {
+  const result = [];
+  const path = [];
+  let sum = 0;
+
+  const backtracking = (candidates, target, startIndex) => {
+    if (sum > target) return;
+    if (sum === target) {
+      result.push(path.slice());
+      return;
+    }
+    for (let i = startIndex; i < candidates.length; i++) {
+      let curr = candidates[i];
+      path.push(curr);
+      sum += curr;
+      backtracking(candidates, target, i);
+      sum -= curr;
+      path.pop();
+    }
+  };
+  backtracking(candidates, target, 0);
+
+  return result;
+};