谷歌笔试题“滑动解锁”深度搜索哪错了？

#include <iostream>
#include <memory>
#include <stdio.h>
#include <stdlib.h>

using namespace std ;

int knows[10][10] ;//保存必须包含的边(已知的折线段)
int record[10][10] ;//相邻的边值为1，不相邻的值为0
int visited[10] ;
int N ; //已知折线段数目

void init(    ) {
	record[1][3] = record[4][6] = record[7][9] = 1;//横着的非相邻顶点
	record[3][1] = record[6][4] = record[9][7] = 1;
	record[1][7] = record[2][8] = record[3][9] = 1;//竖着的非相邻顶点
	record[7][1] = record[1][7] = record[9][3] = 1;
	record[1][9] = record[9][1] = record[3][7] = record[7][3] = 1;//斜着的非相邻顶点
}

int res;
void dfs( int depth ,  int cur  , int contains  ) {

	if ( depth >= 4 ) {
		if (contains == N)//看到的边全部包含
			res++;
		//不返回，因为要在当前基础上继续扩展
	}

	for (int i = 1; i <= 9; ++i) {
		if ( visited[ i ] == 0 ) {
			visited[ i ] = 1 ;
			
			if (knows[cur][i] == 1)//如果这条边是必须走的边
				contains++ ;
                        //如果是相邻顶点，或者非相邻顶点但是中间顶点已经走过了
			if(  record[cur][i]==0 ||  ( record[cur][i]==1 && visited[ (cur+i)/2 ]==1   )         )
				 dfs(  depth + 1, N, contains) ;

			//回溯，取消这条边
			visited[ i ] = 0 ;
			if (knows[cur][i] == 1)//如果这条边是必须走的边
				contains-- ;
		}
	}
	//cout << res << endl;
}

int main(   )
{
	int T ;//测试数据组数
	cin >> T;
	while ( T-- ) {
		cin >> N;

		memset(record, 0, sizeof(record));
		init(  ) ;
		memset(knows, 0, sizeof(knows));

		for (int i = 0; i < N; ++i) {
			int x, y; 
			cin >> x >> y;
			knows[x][y] = knows[y][x] = 1 ;
		}
	
		res = 0 ;

		for ( int i = 1; i <= 9; ++i ) {//从当前i顶点出发
			memset( visited, 0, sizeof(visited) ) ;
			
			visited[ i ] = 1; //i顶点已走因此depth=1
			dfs(1, i, 0);
			
			visited[ i ] = 0 ;
		}
		cout << res<< endl;
	}
	return 0 ;
}