题解 | #牛群分层排列#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return string字符串vector
     */
    vector<string> levelOrder(TreeNode* root) 
    {
        // write code here
        vector<string> result;
        if (root == NULL)
        {
            return result;
        }
        queue<TreeNode*> que;
        que.push(root);
        while(!que.empty())
        {
            int n = que.size();
            string ans = "";
            for (int i = 0;i < n;++i)
            {
                TreeNode* node = que.front();
                que.pop();
                ans += to_string(node->val);
                if (node->left)
                {
                    que.push(node->left);
                }
                if (node->right)
                {
                    que.push(node->right);
                }
            }
            result.push_back(ans);
        }
        return result;
    }
};