#include "stdio.h"
#define maxium 100
int s[maxium];
  int first[maxium];
  int last[maxium];
typedef struct graph{
   int data[maxium][maxium];
   int n;
}graph;

graph inputgraph(int x)
{ int i,j;
  graph g; 
   g.n=x;
  for(i=1;i<=g.n;i++)
  {   printf("输入第%d个节点",i);
	  for(j=1;j<=g.n;j++)
		  scanf("%d",&g.data[i][j]);
  }	  
	  return g;
}

void change(graph g )	
{
  int i,j,count=0;
  for(i=0;i<g.n;i++)
	  first[i]=last[i]=0;
  for(i=1;i<=g.n;i++)
  { for(j=1;j<=g.n;j++)
       if(g.data[i][j])
	      { count++; 
	       if(count==1)
		   { s[first[i]=(last[i-1]++)]=j;
		     last[i]=first[i];
		   }
           else 
			   s[++last[i]]=j;
	      }
       else 
	      last[i]=-1;
	 count=0;
  } 
}

int judge(int i)
{  
   if(i<0)i=-i; 
       if(first[i]>last[i]) return 0;
       else
	   {int j;
         for(j=first[i];j<=last[i];j++)
		 {if(s[j])
		    {s[j]=-s[j]; 	   
	        judge(s[j]);
		     }
	       else return 1;  
		 }	 
	   }
   
}
 void main()
 { graph g;
  int n;
  printf("输入图的顶点数：");
  scanf("%d",&n);
  g=inputgraph(n);
  change(g);
  if(judge(1)) printf("图中存在回路");
  else printf("图中不存在回路"); 
}

judge 有错误：stack overflow
应该怎么改正呢？
谢谢！