标签：des style blog color io for ar div
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]
]
思路：每次从后往前对当前层元素进行遍历，这样每层将交替出现顺序、逆序。在保存下一层节点时：如果当前层的元素是顺序的，则应先加入左节点再加入右节点；否则，应先加入右节点再加入左节点。
1 class Solution { 2 public: 3 vector<vector<int>> zigzagLevelOrder( TreeNode *root ) { 4 vector<vector<int>> zigzags; 5 vector<TreeNode*> nodeList; 6 if( root ) { nodeList.push_back( root ); } 7 while( !nodeList.empty() ) { 8 vector<TreeNode*> newNodeList; 9 vector<int> values; 10 for( auto iter = nodeList.rbegin(); iter != nodeList.rend(); ++iter ) { 11 values.push_back( (*iter)->val ); 12 if( (*iter)->left ) { newNodeList.push_back( (*iter)->left ); } 13 if( (*iter)->right ) { newNodeList.push_back( (*iter)->right ); } 14 } 15 zigzags.push_back( values ); 16 if( newNodeList.empty() ) { break; } 17 nodeList.clear(); values.clear(); 18 for( auto iter = newNodeList.rbegin(); iter != newNodeList.rend(); ++iter ) { 19 values.push_back( (*iter)->val ); 20 if( (*iter)->right ) { nodeList.push_back( (*iter)->right ); } 21 if( (*iter)->left ) { nodeList.push_back( (*iter)->left ); } 22 } 23 zigzags.push_back( values ); 24 } 25 return zigzags; 26 } 27 };
Binary Tree Zigzag Level Order Traversal,布布扣,bubuko.com
Binary Tree Zigzag Level Order Traversal
标签：des style blog color io for ar div
原文地址：http://www.cnblogs.com/moderate-fish/p/3917915.html
