标签：des style blog io ar color sp for on
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] ]
/** * 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> > levelOrder(TreeNode *root) { vector<vector<int> > result; result.clear(); if(root == NULL) return result; vector<TreeNode *> q[2]; int current = 1; int next = 0; q[0].push_back(root); while(q[next].empty() == false) { current = !current; next = !next; vector<int> tempVec; for(auto w : q[current]) { tempVec.push_back(w->val); if(w->left) { q[next].push_back(w->left); } if(w->right) { q[next].push_back(w->right); } } result.push_back(tempVec); tempVec.clear(); q[current].clear(); } return result; } };
解题思路：层次遍历，在处理层次遍历的代码中，巧妙的运用2个向量保存当前正在处理的层的节点q[current]，和该层节点的儿子所组成的下一层节点q[next]在处理开始将current和next互换，轻松实现层次切换。再有就是遍历向量的写法for(auto w :q[current])是c++11的新特性，在编译器中不用通过。
LeetCode Binary Tree Level Order Traversal
标签：des style blog io ar color sp for on
原文地址：http://www.cnblogs.com/55open/p/4134884.html
