标签：des style blog color io 数据 for ar
Given a binary tree, return the bottom-up level order traversal of its nodes‘ values. (ie, from left to right, level by level from leaf to root).
For example:
Given binary tree {3,9,20,#,#,15,7},
3
/ 9 20
/ 15 7
return its bottom-up level order traversal as:
[
[15,7],
[9,20],
[3]
]
思路：对输入二叉树进行广度优先遍历。得到root-to-leaf次序的每一层的数据，其逆序即为leaf-to-root的结果。
1 class Solution { 2 public: 3 vector<vector<int>> levelOrderBottom( TreeNode *root ) { 4 vector<vector<int>> levels; 5 if( !root ) { return levels; } 6 vector<TreeNode*> nodes( 1, root ); 7 while( !nodes.empty() ) { 8 vector<TreeNode*> new_nodes; 9 vector<int> values; 10 for( auto iter = nodes.begin(); iter != nodes.end(); ++iter ) { 11 values.push_back( (*iter)->val ); 12 if( (*iter)->left ) { new_nodes.push_back( (*iter)->left ); } 13 if( (*iter)->right ) { new_nodes.push_back( (*iter)->right ); } 14 } 15 nodes = new_nodes; 16 levels.push_back( values ); 17 } 18 vector<vector<int>> results; 19 for( size_t i = levels.size(); i != 0; --i ) { 20 results.push_back( levels[i-1] ); 21 } 22 return results; 23 } 24 };
Binary Tree Level Order Traversal II,布布扣,bubuko.com
Binary Tree Level Order Traversal II
标签：des style blog color io 数据 for ar
原文地址：http://www.cnblogs.com/moderate-fish/p/3917741.html
