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(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    vector<vector<int> > Print(TreeNode* pRoot) {
        vector<vector<int>>res;
        if(pRoot==NULL)
        {
            return res;//空的就直接返回一个空的
        }
        int n ;
        queue<TreeNode*>q;
        q.push(pRoot);            //类似于二叉树的层序遍历，只不过需要最后需要反转
        bool flag = true;
        while(!q.empty())
        {
            vector<int>row;
            n = q.size();
            flag = !flag;
            for(int  i = 0;i<n;i++)
            {
                TreeNode*tmp;
                tmp = q.front();
                row.push_back(q.front()->val);
                q.pop();
                if(tmp->left!=NULL)
                {
                    q.push(tmp->left);
                }
                 if(tmp->right!=NULL)
                {
                    q.push(tmp->right);
                }
            }
            if(flag)
                reverse(row.begin(),row.end());
            res.push_back(row);
        }
        return res;

    }

};