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107.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,null,null,15,7],
3 / 9 20 / 15 7
return its bottom-up level order traversal as:
[ [15,7], [9,20], [3]}
/** * 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) { queue<TreeNode *> q; vector<vector<int> > vv; if (root != NULL) { q.push(root); } while(!q.empty()) { int m = q.size(); vector<int> v; while(m > 0) { TreeNode * n = q.front();q.pop(); v.push_back(n->val); TreeNode * left = n->left; TreeNode * right = n->right; if (left != NULL) q.push(left); if (right != NULL) q.push(right); m--; } if(v.size())vv.push_back(v); } reverse(vv.begin(), vv.end()); return vv; }};
树的层次遍历，输出每一层
107.Binary Tree Level Order Traversal II
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