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Binary Tree Level Order Traversal II
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]]
/** * 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> > levelOrderBottom(TreeNode *root) { vector<vector<int> > vec; if(root == NULL) return vec; queue<TreeNode *> crt, wait; crt.push(root); while(crt.size() > 0){ int num = crt.size(); vector<int> arr; while(num--){ TreeNode *tmp = crt.front(); if(tmp->left) wait.push(tmp->left); if(tmp->right) wait.push(tmp->right); arr.push_back(tmp->val); crt.pop(); } vec.insert(vec.begin(), arr); int n = wait.size(); while(n--){ TreeNode *tmp = wait.front(); wait.pop(); crt.push(tmp); } } return vec; }};
Binary Tree Level Order Traversal II
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