up 103. 二叉树的锯齿形层序遍历

Author: rongweihe

algorithms/algo_notes/二叉树合集.md

@@ -23,3 +23,52 @@ public:
     }
 };
 ```
+
+## 103 按Z字形打印二叉�树 https://leetcode-cn.com/problems/binary-tree-zigzag-level-order-traversal/
+
+思路：用一个队列，一个bool标志位实现，每次遍历完取队列头元素之后反转
+
+```c++
+/*
+struct TreeNode {
+    int val;
+    struct TreeNode *left;
+    struct TreeNode *right;
+    TreeNode(int x) :
+            val(x), left(NULL), right(NULL) {
+    }
+};
+*/
+
+class Solution {
+public:
+    std::vector<vector<int> > Print(TreeNode* pRoot) {
+        std::vector<vector<int>> res;
+        if (!pRoot) return res;
+        std::queue<TreeNode*>q;
+        q.push(pRoot);
+        bool even = false;
+        while(!q.empty()) {
+            std::vector<int>vec;
+            const int size = q.size();
+            for(int i = 0; i < size; ++i) {
+                TreeNode* node = q.front();
+                q.pop();
+                vec.push_back(node->val);
+                if (node->left) {
+                    q.push(node->left);
+                }
+                if (node->right) {
+                    q.push(node->right);
+                }
+            }
+            if (even) {
+                std::reverse(vec.begin(), vec.end());
+            }
+            res.push_back(vec);
+            even = !even;
+        }
+        return res;
+    }
+};
+```