leetcode：655. 输出二叉树

/**
 * 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<vector<string>> printTree(TreeNode* root) {
    int i=getTreeHigh(root);    //i行
    int j=pow(2,i)-1;           //j列
    vector<vector<string>> res(i,vector<string>(j,""));    //初始化比for循环赋值要快

    dfs(res,root,0,0,j);
    return res;
    }

    void dfs(vector<vector<string>>& res,TreeNode* t,int depth,int left,int right){
        if(!t)return;
        int mid=left+right>>1;
        res[depth][mid]=to_string(t->val);      //所需要修改的值的下标类似于二分的中间数
                                                //就是区间的中心点
        dfs(res,t->left,depth+1,left,mid);
        dfs(res,t->right,depth+1,mid,right);
    }

    int getTreeHigh(TreeNode* t){       //递归求树的高度
        if(!t)return 0;
        return max(getTreeHigh(t->left),getTreeHigh(t->right))+1;
    }
};