Leetcode 107. Binary Tree Level Order Traversal II

 

 

c++比Binary Tree Level Order Traversal 多了一行reverse函数

/**
 * 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>> ans;
        if(!root) return ans;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()) {
            int len = q.size();
            vector<int> v;
            while(len--) {
                TreeNode *t = q.front();
                q.pop();
                v.push_back(t->val);
                if(t->left) q.push(t->left);
                if(t->right) q.push(t->right);
            }
            ans.push_back(v);
        }
        reverse(ans.begin(), ans.end());
        return ans;
    }
};