Merge branch 'master' of github.com:youngyangyang04/leetcode-master

Author: youngyangyang04

problems/0216.组合总和III.md

@@ -301,22 +301,29 @@ class Solution {
 
 ```py
 class Solution:
-    def combinationSum3(self, k: int, n: int) -> List[List[int]]:
-        res = []  #存放结果集
-        path = []  #符合条件的结果
-        def findallPath(n,k,sum,startIndex):
-            if sum > n: return  #剪枝操作
-            if sum == n and len(path) == k:  #如果path.size() == k 但sum != n 直接返回
-                return res.append(path[:])
-            for i in range(startIndex,9-(k-len(path))+2):  #剪枝操作
-                path.append(i)
-                sum += i 
-                findallPath(n,k,sum,i+1)  #注意i+1调整startIndex
-                sum -= i  #回溯
-                path.pop()  #回溯
-        
-        findallPath(n,k,0,1)
-        return res
+    def __init__(self):
+        self.res = []
+        self.sum_now = 0
+        self.path = []
+
+    def combinationSum3(self, k: int, n: int) -> [[int]]:
+        self.backtracking(k, n, 1)
+        return self.res
+
+    def backtracking(self, k: int, n: int, start_num: int):
+        if self.sum_now > n:  # 剪枝
+            return
+        if len(self.path) == k:  # len(path)==k时不管sum是否等于n都会返回
+            if self.sum_now == n:
+                self.res.append(self.path[:])
+            return
+        for i in range(start_num, 10 - (k - len(self.path)) + 1):
+            self.path.append(i)
+            self.sum_now += i
+            self.backtracking(k, n, i + 1)
+            self.path.pop()
+            self.sum_now -= i
+        return
 ```
 
 ## Go：

problems/二叉树理论基础.md

@@ -227,6 +227,21 @@ function TreeNode(val, left, right) {
 }
 ```
 
+Swift:
+```Swift
+class TreeNode<T> {
+    var value: T
+    var left: TreeNode?
+    var right: TreeNode?
+    init(_ value: T,
+         left: TreeNode? = nil,
+         right: TreeNode? = nil) {
+        self.value = value
+        self.left = left
+        self.right = right
+    }
+}
+```
 
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>