Given 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]
]
confused what "{1,#,2,3}"
means?
> read more on how binary tree is serialized on OJ.
vector<vector<int> > zigzagLevelOrder(TreeNode *root) { //C++ vector<vector<int> > result; if(root == NULL) return result; int toleft = 1; stack<TreeNode*> left; stack<TreeNode*> right; left.push(root); while(!(left.empty()&&right.empty())) { vector<int> vec; if(toleft==1){ while(!left.empty()){ TreeNode* temp = left.top(); vec.push_back(temp->val); if(temp->left != NULL) right.push(temp->left); if(temp->right != NULL) right.push(temp->right); left.pop(); } result.push_back(vec); } else{ while(!right.empty()){ TreeNode* temp = right.top(); vec.push_back(temp->val); if(temp->right != NULL) left.push(temp->right); if(temp->left != NULL) left.push(temp->left); right.pop(); } result.push_back(vec); } toleft *=-1; } return result; }
[leetcode]103 Binary Tree Zigzag Level Order Traversal
原文地址:http://blog.csdn.net/chenlei0630/article/details/42681253