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Given a binary tree, return the level order traversal of its nodes‘ values. (ie, from left to right, level by level).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ 9 20
/ 15 7
return its level order traversal as:
[ [3], [9,20], [15,7] ]
分析：用两个vector分别保存本层和下一层的节点。代码如下：
class Solution { public: vector<vector<int> > levelOrder(TreeNode *root) { vector<vector<int> > result; if(root == NULL) return result; vector<TreeNode *> prev; prev.push_back(root); while(!prev.empty()){ vector<TreeNode *> cur; vector<int> level; for(auto i = prev.begin(); i != prev.end(); i++){ level.push_back((*i)->val); if((*i)->left) cur.push_back((*i)->left); if((*i)->right) cur.push_back((*i)->right); } result.push_back(level); prev = cur; } return result; } };
Leetcode:Binary Tree Level Order Traversal
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原文地址：http://www.cnblogs.com/Kai-Xing/p/4191420.html
