【leetcode 二叉树 C++】107. Binary Tree Level Order Traversal II

107. Binary Tree Level Order Traversal II

/**
 * 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;
        vector<int> V;
        queue<TreeNode*> Q;
        TreeNode* p;
        if(root) Q.push(root);
        while(!Q.empty()) {
    
    
            int len = Q.size();
            V.clear();
            for(int ii = 0; ii < len; ii++) {
    
    
                p = Q.front();
                Q.pop();
                V.push_back(p->val);
                if(p->left) Q.push(p->left);
                if(p->right) Q.push(p->right);
            }
            result.insert(result.begin(), V);
        }
        return result;
    }
};