refactor: 0077.组合.md

problems/0077.组合.md

@@ -499,24 +499,28 @@ var combine = function (n, k) {
 剪枝：
 
 ```javascript
-let result = []
-let path = []
-var combine = function(n, k) {
-  result = []
-  combineHelper(n, k, 1)
-  return result
+var combine = function (n, k) {
+  // 回溯法
+  let result = [],
+    path = [];
+  let backtracking = (_n, _k, startIndex) => {
+    // 终止条件
+    if (path.length === _k) {
+      result.push(path.slice());
+      return;
+    }
+    // 循环本层集合元素
+    for (let i = startIndex; i <= _n - (_k - path.length) + 1; i++) {
+      path.push(i);
+      //   递归
+      backtracking(_n, _k, i + 1);
+      //   回溯操作
+      path.pop();
+    }
+  };
+  backtracking(n, k, 1);
+  return result;
 };
-const combineHelper = (n, k, startIndex) => {
-  if (path.length === k) {
-    result.push([...path])
-    return
-  }
-  for (let i = startIndex; i <= n - (k - path.length) + 1; ++i) {
-    path.push(i)
-    combineHelper(n, k, i + 1)
-    path.pop()
-  }
-}
 ```
 
 ### TypeScript