216. 组合总和 III

Author: w2xi

README.md

@@ -87,6 +87,7 @@
 |203|[移除链表元素](https://leetcode.cn/problems/remove-linked-list-elements/)|[JavaScript](./algorithms/remove-linked-list-elements.js)|Easy|
 |206|[反转链表](https://leetcode-cn.com/problems/reverse-linked-list/)|[JavaScript](./algorithms/reverse-linked-list.js)|Easy|
 |209|[长度最小的子数组](https://leetcode.cn/problems/minimum-size-subarray-sum/)|[JavaScript](./algorithms/minimum-size-subarray-sum.js)|Medium|
+|216|[组合总和 III](https://leetcode.cn/problems/combination-sum-iii/)|[JavaScript](./algorithms/combination-sum-iii.js)|Medium|
 |222|[完全二叉树的节点个数](https://leetcode.cn/problems/count-complete-tree-nodes/)|[JavaScript](./algorithms/count-complete-tree-nodes.js)|Medium|
 |225|[用队列实现栈](https://leetcode.cn/problems/implement-stack-using-queues/)|[JavaScript](./algorithms/implement-stack-using-queues.js)|Easy|
 |226|[翻转二叉树](https://leetcode.cn/problems/invert-binary-tree/)|[JavaScript](./algorithms/invert-binary-tree.js)|Easy|

algorithms/combination-sum-iii.js

@@ -0,0 +1,34 @@
+/**
+ * 216. 组合总和 III
+ * @param {number} k
+ * @param {number} n
+ * @return {number[][]}
+ */
+var combinationSum3 = function (k, n) {
+  const result = [];
+  const path = [];
+  let sum = 0;
+
+  const backtracking = (k, n, startIndex) => {
+    if (sum > n) {
+      // 剪枝 ( 和已经大于 n 了, 继续往后遍历没有意义 )
+      return;
+    }
+    if (path.length === k) {
+      if (sum === n) {
+        result.push(path.slice());
+      }
+      return;
+    }
+    for (let i = startIndex; i <= 9; i++) {
+      path.push(i);
+      sum += i;
+      backtracking(k, n, i + 1, sum);
+      sum -= i;
+      path.pop();
+    }
+  };
+  backtracking(k, n, 1);
+
+  return result;
+};