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.
/** * 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>> res; vector<int> tmp; stack<TreeNode *> Spre,Scurr; if(root==NULL)return res; else { int flag=0; Spre.push(root); while(1) { flag++; while(!Spre.empty()) { TreeNode *tem=Spre.top(); Spre.pop(); tmp.push_back(tem->val); if(flag%2==1) { if(tem->left)Scurr.push(tem->left); if(tem->right)Scurr.push(tem->right); } else { if(tem->right)Scurr.push(tem->right); if(tem->left)Scurr.push(tem->left); } } res.push_back(tmp); tmp.clear(); if(Scurr.empty())break; else Scurr.swap(Spre); } return res; } } };