题解 | #从上往下打印二叉树# | 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> ans;
		queue<TreeNode*> q;
		if (root) {
			q.push(root);
		}
		while (!q.empty()) {
			int n = q.size();
			while (n-- >= 1) {
				ans.push_back(q.front()->val);
				if (q.front()->left) q.push(q.front()->left);
				if (q.front()->right) q.push(q.front()->right);
				q.pop();
			}
		}
		return ans;
    }
};