学步园

思路：深搜判定图连通+欧拉回路判定

#include "string.h"
#include "stdio.h"
#define M 25
int a[M][M];
int visit[M];
int count,n;
int DFS (int x);
int main ()
{
    int
m,i,j,k;
    while (scanf
("%d %d",&n,&m)!= EOF)
    {
       
memset (a,0,sizeof(a));
       
memset (visit,0,sizeof(visit));
       
count =0;
       
for (k = 0; k < m; k ++)
       
{
           
scanf ("%d %d",&i,&j);
           
a[i-1][j-1] = 1;  //有重边
       
}
       
if (n == 1)
           
printf ("Yes\n");
       
else
       
{
           
if (DFS (0))
               
printf ("Yes\n");
           
else
               
printf ("No\n");
       
}
    }
}

int DFS (int x)  //判定连通性
{
    int i;
    for (i = 0;
i < n; i ++)
    {
       
if (a[x][i]&&visit[i] == 0)
       
{
           
count ++;
           
visit[i] = 1;
           
DFS (i);
       
}
    }
    if
(count==n)
       
return 1;
    else