LintCode-71.二叉树的锯齿形层次遍历

二叉树的锯齿形层次遍历

给出一棵二叉树，返回其节点值的锯齿形层次遍历（先从左往右，下一层再从右往左，层与层之间交替进行）

样例

给出一棵二叉树 {3,9,20,#,#,15,7},

返回其锯齿形的层次遍历为：
[
    [3],
    [20,9],
    [15,7]
]

标签

领英 二叉树 队列 二叉树遍历 宽度优先搜索

code

/**
* Definition of TreeNode:
* class TreeNode {
* public:
* int val;
* TreeNode *left, right;
* TreeNode(int val) {
* this->val = val;
* this->left = this->right = NULL;
* }
* }
/
class Solution {
/
* @param root: The root of binary tree.
* @return: A list of lists of integer include
* the zigzag level order traversal of its nodes' values
*/
public:
vector<vector> zigzagLevelOrder(TreeNode root) {
// write your code here
vector<vector > order;
queue<TreeNode> queue;
int len,leaver=1;

if(root == NULL) {
return order;
}

queue.push(root);
len = queue.size();

while(!queue.empty()) {
vector base;
len = queue.size();

while(len--) {
TreeNode *tmp=queue.front();
base.push_back(tmp->val);
queue.pop();
if(tmp->right)
queue.push(tmp->right);
if(tmp->left)
queue.push(tmp->left);
}

if(leaver%2 == 1)
reverse(base.begin(),base.end());
order.push_back(base);
leaver++;
}
return order;
}
};