题解 | #求二叉树的层序遍历# | C++

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
#include <vector>
#include <queue>
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 int整型vector<vector<>>
     */
    vector<vector<int> > levelOrder(TreeNode* root) {
        vector<vector<int>> ans;
        if (root == nullptr) return ans;
        queue<TreeNode*> q;
        q.push(root);
        while (!q.empty()) {
            int n = q.size();
            vector<int> item;
            while (n-- >= 1) {
                auto f = q.front();
                item.push_back(f->val);
                if (f->left) q.push(f->left);
                if (f->right) q.push(f->right);
                q.pop();
            }
            ans.push_back(std::move(item));
        }
        return ans;
    }
};