Merge pull request #1695 from L1Y1/master

Update 0235.二叉搜索树的最近公共祖先.md

problems/0216.组合总和III.md

@@ -416,24 +416,31 @@ func backTree(n,k,startIndex int,track *[]int,result *[][]int){
  * @return {number[][]}
  */
 var combinationSum3 = function(k, n) {
-    const backtrack = (start) => {
+    let res = [];
-        const l = path.length;
+    let path = [];
-        if (l === k) {
+    let sum = 0;
-            const sum = path.reduce((a, b) => a + b);
+    const dfs = (path,index) => {
-            if (sum === n) {
+        // 剪枝操作
+        if (sum > n){
+            return 
+        }
+        if (path.length == k) {
+            if(sum == n){
                 res.push([...path]);
+                return 
             }
-            return;
         }
-        for (let i = start; i <= 9 - (k - l) + 1; i++) {
+        for (let i = index; i <= 9 - (k-path.length) + 1;i++) {
             path.push(i);
-            backtrack(i + 1);
+            sum = sum + i;
-            path.pop();
+            index += 1;
+            dfs(path,index);
+            sum -= i
+            path.pop()
         }
     }
-    let res = [], path = [];
+    dfs(path,1);
-    backtrack(1);
+    return res
-    return res;
 };
 ```
 

problems/0235.二叉搜索树的最近公共祖先.md

@@ -328,13 +328,11 @@ var lowestCommonAncestor = function(root, p, q) {
     }
     if(root.val>p.val&&root.val>q.val) {
         // 向左子树查询
-        let left = lowestCommonAncestor(root.left,p,q);
+         return root.left = lowestCommonAncestor(root.left,p,q);
-        return left !== null&&left;
     }
     if(root.val<p.val&&root.val<q.val) {
         // 向右子树查询
-        let right = lowestCommonAncestor(root.right,p,q);
+        return root.right = lowestCommonAncestor(root.right,p,q);
-        return right !== null&&right;
     }
     return root;
 };