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BinaryTreeZigzagLevelOrderTraversal.cpp
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BinaryTreeZigzagLevelOrderTraversal.cpp
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/*
iven a binary tree, return the zigzag level order traversal of its nodes' values.
(ie, from left to right, then right to left for the next level and alternate between).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ \
9 20
/ \
15 7
return its zigzag level order traversal as:
[
[3],
[20,9],
[15,7]
]
*/
class Solution {
public:
vector<vector<int> > zigzagLevelOrder(TreeNode *root) {
vector<vector<int>> result;
if(!root)
return result;
vector<TreeNode*> level;
level.push_back(root);
bool zig = false;
while(!level.empty())
{
vector<TreeNode*> next;
vector<int> V;
for(int i=0;i<level.size();i++)
{
V.push_back(level[i]->val);
if(level[i]->left)
next.push_back(level[i]->left);
if(level[i]->right)
next.push_back(level[i]->right);
}
if(zig){
reverse(V.begin(),V.end());
}
zig = !zig;//Do not forget
result.push_back(V);
level = next;
}
}
};