剑指 Offer 32 - I. 从上到下打印二叉树_c语言请你设计一个程序实现从上到下打印出二叉树的每个节点,同一层的节点按照从左到右

解法一

层次遍历

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> levelOrder(TreeNode* root) {
        queue<TreeNode*> que;
        vector<int> res;
        que.push(root);
        if(!root) return res;
        TreeNode* temp;
        while (!que.empty())
        {
            temp = que.front();
            que.pop();
            res.push_back(temp->val);
            if(temp->left) que.push(temp->left);
            if(temp->right) que.push(temp->right);
        }
        return res;
    }
}; 
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