题解 | #从上往下打印二叉树#

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

		}
		return out;
    }
};

使用队列queue实现二叉树的层次遍历