牛客网刷题|从上往下打印二叉树

这个题在leetcode里也有的
题目大意：
从上往下打印出二叉树的每个节点，同层节点从左至右打印。
c++

*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/

class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        vector<int> ret;
        queue<struct TreeNode *> que;
        que.push(root);
        while (!que.empty()) {
            auto now = que.front();
            que.pop();
            if (now == nullptr)
                continue;
            ret.push_back(now->val);
            que.push(now->left);
            que.push(now->right);
        }
        return ret;
    }
};

上面是科班出身写的
我写的就比较随意化，一样的思路，两个地方简化了

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
class Solution {
public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        queueque;
        vector<int>ret;
        que.push(root);
        while(!que.empty())
        {
            TreeNode* temp = que.front();
            que.pop();
            if(temp==nullptr)
                continue;
            ret.push_back(temp->val);
            que.push(temp->left);
            que.push(temp->right);
        }
        return ret;
    }
};