添加·216.组合总和IIIJavaScript版本

problems/0216.组合总和III.md

@@ -180,7 +180,7 @@ if (sum > targetSum) { // 剪枝操作
 
 最后C++代码如下：
 
-```
+```c++
 class Solution {
 private:
     vector<vector<int>> result; // 存放结果集
@@ -262,7 +262,7 @@ class Solution {
 ```
 
 Python：
-```python3
+```py
 class Solution:
     def combinationSum3(self, k: int, n: int) -> List[List[int]]:
         res = []  #存放结果集
@@ -284,6 +284,44 @@ class Solution:
 
 Go：
 
+javaScript:
+
+```js
+// 等差数列
+var maxV = k => k * (9 + 10 - k) / 2;
+var minV = k => k * (1 + k) / 2;
+var combinationSum3 = function(k, n) {
+    if (k > 9 || k < 1) return [];
+    // if (n > maxV(k) || n < minV(k)) return [];
+    // if (n === maxV(k)) return [Array.from({length: k}).map((v, i) => 9 - i)];
+    // if (n === minV(k)) return [Array.from({length: k}).map((v, i) => i + 1)];
+
+    const res = [], path = [];
+    backtracking(k, n, 1, 0);
+    return res;
+    function backtracking(k, n, i, sum){
+        const len = path.length;
+        if (len > k || sum > n) return;
+        if (maxV(k - len) < n - sum) return;
+        if (minV(k - len) > n - sum) return; 
+
+        if(len === k && sum == n) {
+            res.push(Array.from(path));
+            return;
+        }
+
+        const min = Math.min(n - sum, 9 + len - k + 1);
+
+        for(let a = i; a <= min; a++) {
+            path.push(a);
+            sum += a;
+            backtracking(k, n, a + 1, sum);
+            path.pop();
+            sum -= a;
+        }
+    }
+};
+```