题目描述

blablabla

样例

blablabla

算法1

用两个栈做的

C++ 代码

#include<queue>
class Solution {
public:
    stack<TreeNode*> a, b;
    vector<vector<int>> dat;
    vector<vector<int>> printFromTopToBottom(TreeNode* root) {
        a.push(root);
        while (!a.empty() || !b.empty()) {
            vector<int> temp;
            while (!a.empty()) {
                if (a.top()) {
                    auto x = a.top();
                    temp.push_back(x->val);
                    b.push(x->left);
                    b.push(x->right);
                }
                a.pop();
            }
            if (!temp.empty()) {
                dat.push_back(temp);
            }

            temp.clear();
            while (!b.empty()) {
                if (b.top()) {
                    auto x = b.top();
                    temp.push_back(x->val);
                    a.push(x->right);
                    a.push(x->left);
                }
                b.pop();
            }
            if (!temp.empty()) {
                dat.push_back(temp);
            }
        }
        return dat;
    }
};