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

problems/0102.二叉树的层序遍历.md

@@ -2532,20 +2532,18 @@ class Solution:
             return 0
 
         queue_ = [root]
-        result = []
+        depth = 0
         while queue_:
             length = len(queue_)
-            sub = []
             for i in range(length):
                 cur = queue_.pop(0)
                 sub.append(cur.val)
                 #子节点入队列
                 if cur.left: queue_.append(cur.left)
                 if cur.right: queue_.append(cur.right)
-            result.append(sub)
+            depth += 1
 
-
-        return len(result)
+        return depth
 ```
 
 Go：

problems/0150.逆波兰表达式求值.md

@@ -163,6 +163,25 @@ class Solution {
 
 python3
 
+```python
+from operator import add, sub, mul
+
+class Solution:
+    op_map = {'+': add, '-': sub, '*': mul, '/': lambda x, y: int(x / y)}
+
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        for token in tokens:
+            if token not in {'+', '-', '*', '/'}:
+                stack.append(int(token))
+            else:
+                op2 = stack.pop()
+                op1 = stack.pop()
+                stack.append(self.op_map[token](op1, op2))  # 第一个出来的在运算符后面
+        return stack.pop()
+```
+
+另一种可行，但因为使用eval相对较慢的方法:
 ```python
 class Solution:
     def evalRPN(self, tokens: List[str]) -> int:

problems/0222.完全二叉树的节点个数.md

@@ -188,7 +188,7 @@ public:
 
 ```CPP
 if (root == nullptr) return 0; 
-// 开始根据做深度和有深度是否相同来判断该子树是不是满二叉树
+// 开始根据左深度和右深度是否相同来判断该子树是不是满二叉树
 TreeNode* left = root->left;
 TreeNode* right = root->right;
 int leftDepth = 0, rightDepth = 0; // 这里初始为0是有目的的，为了下面求指数方便
@@ -843,3 +843,4 @@ impl Solution {
 <a href="https://programmercarl.com/other/kstar.html" target="_blank">
   <img src="../pics/网站星球宣传海报.jpg" width="1000"/>
 </a>
+