剑指offer - 从上往下打印二叉树

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题目

https://www.nowcoder.com/questionTerminal/7fe2212963db4790b57431d9ed259701

题意

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。

题解

二叉树的层次遍历。

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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;
        if(root==NULL) return ans;
        queue<TreeNode *> que;
        que.push(root);
        while(!que.empty()){	
            TreeNode * node = que.front();
            ans.push_back(node->val);
            que.pop();
            if(node->left)
                que.push(node->left);
            if(node->right)
                que.push(node->right);
        }
        return ans;
    }
};