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Binary_Tree_Zigzag_Level_Order_Traversal.cpp
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Binary_Tree_Zigzag_Level_Order_Traversal.cpp
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/**
* Definition for binary tree
* 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) {
vector <vector <int> > result;
if(!root) return result;
queue < pair <TreeNode*, int> > Q;
int prev_level = 0, curr_level;
vector <int> container;
Q.push(make_pair(root, 1));
int zigzag = 0;
while(!Q.empty()) {
pair<TreeNode*, int> node = Q.front();
Q.pop();
TreeNode *curr = node.first;
curr_level = node.second;
if(curr_level > prev_level) {
if(container.size() > 0) {
if(zigzag) reverse(container.begin(), container.end());
result.push_back(container);
zigzag ^= 1;
}
container.clear();
}
container.push_back(curr->val);
if(curr->left) Q.push(make_pair(curr->left, curr_level + 1));
if(curr->right) Q.push(make_pair(curr->right, curr_level + 1));
prev_level = curr_level;
}
if(container.size() > 0) {
if(zigzag) reverse(container.begin(), container.end());
result.push_back(container);
}
return result;
}
};