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binary-tree-zigzag-level-order-traversal(AC).cpp
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binary-tree-zigzag-level-order-traversal(AC).cpp
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// 1AC, excellent!!
/**
* 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) {
int i;
for(i = 0; i < result.size(); ++i){
result[i].clear();
}
result.clear();
if(root == nullptr){
return result;
}
preOrder(root, 0);
for(i = 0; i < result.size(); ++i){
if(i % 2){
reverse(result[i], 0, result[i].size() - 1);
}
}
return result;
}
private:
vector<vector<int>> result;
void preOrder(TreeNode *root, int height) {
if(root == nullptr){
return;
}
while(result.size() <= height){
result.push_back(vector<int>());
}
result[height].push_back(root->val);
if(root->left != nullptr){
preOrder(root->left, height + 1);
}
if(root->right != nullptr){
preOrder(root->right, height + 1);
}
}
void reverse(vector<int> &num, int left, int right) {
int i;
if(left >= right){
return;
}
int tmp;
i = left;
while(i < left + right - i){
tmp = num[i];
num[i] = num[left + right - i];
num[left + right - i] = tmp;
++i;
}
}
};