ZOJ 1060 Sorting It All Out(POJ 1094)(关系闭包+计数排序)

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define N 30
struct node
{
int id,in;
}p
;
int cmp(const void *a,const void *b)
{
struct node *aa=(struct node *)a;
struct node *bb=(struct node *)b;
return aa->in > bb->in?1:-1;
}
int map

,n;
void floyd()
{
int i,j,k;
for(k=0;k<n;k++)
{
for(i=0;i<n;i++)
for(j=0;j<n;j++)
map[i][j]=map[i][j]||map[i][k]&&map[k][j];
}
}
int f_huan()
{
int i;
for(i=0;i<n;i++)
if(map[i][i])
return 1;
return 0;
}
int f_xu()
{
int i,j;
for(i=0;i<n;i++)
p[i].id=i,p[i].in=0;
for(j=0;j<n;j++)
{
for(i=0;i<n;i++)
if(map[i][j])
p[j].in++;
}
qsort(p,n,sizeof(p[0]),cmp);
for(i=0;i<n-1;i++)
if(p[i].in==p[i+1].in)
return 0;
return 1;
}
int main()
{
int i,m,huan,xu,phuan,pxu;
char str[4];
while(scanf("%d%d",&n,&m),n+m)
{
memset(map,0,sizeof(map));
huan=xu=phuan=pxu=0;
for(i=1;i<=m;i++)
{
scanf("%s",str);
map[str[0]-'A'][str[2]-'A']=1;
floyd();
if(huan)continue;
if(xu)continue;
huan=f_huan();  //1表示有环
if(huan){phuan=i;continue;}
xu=f_xu();     //1表示完成排序
if(xu)pxu=i;
}
if(huan)
printf("Inconsistency found after %d relations",phuan);
else if(xu)
{
printf("Sorted sequence determined after %d relations: ",pxu);
for(i=0;i<n;i++)
printf("%c",'A'+p[i].id);
}
else printf("Sorted sequence cannot be determined");
puts(".");
}
return 0;
}