POJ 1094 C++ （图论）
//用DFS进行拓扑排序，超时 ，只能重写#include"stdio.h"
#include"string.h"
#include"stdlib.h"
int map[26][26],v[26],used[26],flag,n,total;
char str[27];
void sort(int i,int m)
{ int k;
if(total==n)
{ flag=2;
return ;
}
for(k=0;k<n && !flag;k++)
{ if(map[i][k]==0)
continue;
if(v[k])
{ flag=1;
return ;
}
str[m]=k+65;
total++;
v[k]=1;
sort(k,m+1);
if(flag)
return ;
v[k]=0;
total--;
}
}
int main()
{int row,i,j,a,b,k,l;
char s[4];
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
while(1)
{ scanf("%d%d",&n,&row);
if(n==0 && row==0)
break;
flag=0;
memset(map,0,sizeof(map));
memset(used,0,sizeof(used));
for(k=1;k<=row;k++)
{ scanf("%s",s);
if(!flag)
{memset(v,0,sizeof(v));
a=s[0]-65;
b=s[2]-65;
used[a]=1;
used[b]=1;
map[a][b]=1;
for(i=0;i<n && !flag;i++)
{ if(used[i]==0)
break;
total=1;
v[i]=1;
str[0]=i+65;
sort(i,1);
v[i]=0;
}
if(flag==1)
printf("Inconsistency found after %d relations.\n",k);
else if(flag==2)
{printf("Sorted sequence determined after %d relations: ",k);
for(i=0;i<n;i++)
printf("%c",str[i]);
printf(".\n");
flag=1;
}
}
}
if(!flag)
printf("Sorted sequence cannot be determined.\n");
}
return 0;
}
// 改用floyd_warshall算法才过
#include"stdio.h"
#include"string.h"
#include"stdlib.h"
typedef struct Node{
int d;
char c;
}Node;
int map[26][26],used[26],flag,n;
Node node[26];
int cmp(const void *a, const void *b)
{ return (*(Node *)a).d-(*(Node *)b).d;
}
void check()
{int i,j;
for(i=0;i<n;i++)
{ if(used[i]==0)
return ;
for(j=0;j<n;j++)
if(map[i][j])
node[j].d++;
}
qsort(node,n,sizeof(Node),cmp);
for(i=0;i<n;i++)
if(node[i].d!=i)
return ;
flag=2;
}
int main()
{int row,i,j,a,b,k,h;
char s[4];
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
while(1)
{ scanf("%d%d",&n,&row);
if(n==0 && row==0)
break;
flag=0;
memset(map,0,sizeof(map));
for(h=1;h<=row;h++)
{ scanf("%s",s);
if(!flag)
{a=s[0]-65;
b=s[2]-65;
used[a]=1;
used[b]=1;
for(i=0;i<n;++i)
{node[i].d=0;
node[i].c=i+65;
}
if(map[b][a]==1 || a==b)
{ printf("Inconsistency found after %d relations.\n",h);
flag=1;
}
else
map[a][b]=1;
for(k=0;k<26;++k)
for(i=0;i<26;++i)
for(j=0;j<26;++j)
map[i][j]=(map[i][j]||(map[i][k]&&map[k][j]));
if(!flag)
check();
if(flag==2)
{printf("Sorted sequence determined after %d relations: ",h);
for(i=0;i<n;i++)
printf("%c",node[i].c);
printf(".\n");
}
}
}
if(!flag)
printf("Sorted sequence cannot be determined.\n");
}
return 0;
}
