C++：從上往下打印出二叉樹的每個節點，同層節點從左至右打印。

題目描述

從上往下打印出二叉樹的每個節點，同層節點從左至右打印。

提交代碼：

class Solution {
public:
	vector<int> PrintFromTopToBottom(TreeNode* root) {
		vector<TreeNode> v_in;
		vector<int> v_out;
		if (root==NULL)
		{
			return v_out;
		}
		v_in.push_back(*root);
		while (!v_in.empty())
		{
			TreeNode t1 = v_in.front();
			v_in.erase(v_in.begin());
			if (t1.left!=NULL)
			{
				v_in.push_back(*t1.left);
			}
			if (t1.right != NULL)
			{
				v_in.push_back(*t1.right);
			}
			v_out.push_back(t1.val);
		}
		return v_out;
	}
};

測試代碼：

int main()
{
	Solution* s = new Solution();
	TreeNode* t1 = new TreeNode(1);
	TreeNode* t2 = new TreeNode(2);
	TreeNode* t3 = new TreeNode(3);
	TreeNode* t4 = new TreeNode(4);
	TreeNode* t5 = new TreeNode(5);
	t1->left = t2;
	t1->right = t3;
	t2->left = t4;
	t2->right = t5;
	s->PrintFromTopToBottom(t1);
	//cout <<  << endl;
	system("pause");
	return 0;
}

結果展示：