Leetcode 107. Binary Tree Level Order Traversal II | | Leetcode 107. Binary Tree Level Order Traversal II 文章作者:Tyan博客:noahsnail.com | CSDN | 简书 1. Description 2. Solution Version 1 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public: vector<vector<int>> levelOrderBottom(TreeNode* root) { vector<vector<int>> result; if(!root) { return result; } queue<TreeNode*> q; q.push(root); traverseLevel(q, result); reverse(result.begin(), result.end()); return result; } private: void traverseLevel(queue<TreeNode*>& q, vector<vector<int>>& result) { vector<int> values; int size = q.size(); while(size) { TreeNode* current = q.front(); q.pop(); if(current) { values.push_back(current->val); if(current->left) { q.push(current->left); } if(current->right) { q.push(current->right); } } size--; } result.push_back(values); if(!q.empty()) { traverseLevel(q, result); } }}; Version 2 12345678910111213141516171819202122232425262728293031323334353637/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public: vector<vector<int>> levelOrderBottom(TreeNode* root) { vector<vector<int>> result; if(!root) { return result; } depthLevel(result, root, 0); reverse(result.begin(), result.end()); return result; } private: void depthLevel(vector<vector<int>>& result, TreeNode* root, int depth) { if(!root) { return; } depth++; if(depth > result.size()) { vector<int> values; result.emplace_back(values); } depthLevel(result, root->left, depth); depthLevel(result, root->right, depth); result[depth - 1].push_back(root->val); }}; Reference https://leetcode.com/problems/binary-tree-level-order-traversal-ii/description/ 如果有收获,可以请我喝杯咖啡! 赏 微信打赏 支付宝打赏