题解 | #按之字形顺序打印二叉树#

/**
 * 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 pRoot TreeNode类 
     * @return int整型vector<vector<>>
     */
    vector<vector<int> > Print(TreeNode* pRoot) 
    {
        // write code here
        vector<vector<int>> ans;
        if (pRoot == NULL)
        {
            return ans;
        }
        queue<TreeNode* > que;
        que.push(pRoot);
        int cnt = 0;
        while(!que.empty())
        {
            int size = que.size();
            vector<int> res;
            for (int i = 0;i < size;i++)
            {
                TreeNode* node = que.front();
                que.pop();
                res.push_back(node->val);
                if (node->left) que.push(node->left);
                if (node->right) que.push(node->right);
            }
            if (cnt % 2 == 1)
            {
                reverse(res.begin(),res.end());
            }
            ans.push_back(res);
            cnt += 1;
        }
        return ans;
    }
};