题解 | #从上往下打印二叉树#层次遍历 队列

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};*/
#include <iterator>
class Solution {
  public:
    vector<int> PrintFromTopToBottom(TreeNode* root) {
        queue<TreeNode*>que;
        vector<int> result;
        TreeNode* t;
        if(!root){
            return result;
        }
        que.push(root);
        while(!que.empty()){
            t = que.front();
            result.push_back(t->val);
            if(t->left){
                que.push(t->left);
            }
            if(t->right){
                que.push(t->right);
            }
            que.pop();
        }
        return result;
    }
};