103. Binary Tree Zigzag Level Order Traversal

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int>> zigzagLevelOrder(TreeNode* root) {
bool lefttoright=true;
vector<vector<int>> ret;
queue<TreeNode *> q;
if(!root)
return ret;
q.push(root);
while(!q.empty())
{
int size=q.size();
vector<int> temp(size);
//遍历这一层
for(int i=0;i<size;i++)
{
TreeNode *n=q.front();
q.pop();
int index=lefttoright?i:size-1-i;
temp[index]=n->val;
if(n->left)
q.push(n->left);
if(n->right)
q.push(n->right);
}
//反转遍历顺序
lefttoright=!lefttoright;
ret.push_back(temp);
}
return ret;
}
};