hust 1017 Exact cover 精确覆盖

/*Problem: HUST 1017   User: zyzamp
Memory: 1924 KB   Time: 268 MS
Language: C++   Result: Accepted */
# include<stdio.h>
# include<string.h>
# include<time.h>
# define N 1005
# define V 102005
int U[V],D[V];
int L[V],R[V];
int C[V];
int H
,S
,mark[V];
int size,n,m,OK
,flag;
void Link(int r,int c)
{
S[c]++;C[size]=c;
U[size]=U[c];D[U[c]]=size;
D[size]=c;U[c]=size;
if(H[r]==-1) H[r]=L[size]=R[size]=size;
else
{
L[size]=L[H[r]];R[L[H[r]]]=size;
R[size]=H[r];L[H[r]]=size;
}
mark[size]=r;
size++;
}
void remove(int c)//删除列
{
int i,j;
L[R[c]]=L[c];
R[L[c]]=R[c];
for(i=D[c];i!=c;i=D[i])
{
for(j=R[i];j!=i;j=R[j])
{
U[D[j]]=U[j],D[U[j]]=D[j];
S[C[j]]--;
}
}
}
void resume(int c)
{
int i,j;
for(i=U[c];i!=c;i=U[i])
{
for(j=L[i];j!=i;j=L[j])
{
U[D[j]]=j;D[U[j]]=j;
S[C[j]]++;
}
}
L[R[c]]=c;
R[L[c]]=c;
}
void Dance(int k)
{
int i,j,Min,c;
if(!R[0])
{
flag=1;
printf("%d",k);
for(i=0;i<k;i++)
printf(" %d",mark[OK[i]]);
printf("\n");
return;
}
for(Min=N,i=R[0];i;i=R[i])
if(S[i]<Min) Min=S[i],c=i;
remove(c);//删除该列
for(i=D[c];i!=c;i=D[i])
{
OK[k]=i;
//remove(i);
for(j=R[i];j!=i;j=R[j])
remove(C[j]);
Dance(k+1);
if(flag) return;
for(j=L[i];j!=i;j=L[j])
resume(C[j]);
//resume(i);
}
resume(c);
}
int main()
{
int i,j,num;
while(scanf("%d%d",&n,&m)!=EOF)
{
for(i=0;i<=m;i++)
{
S[i]=0;
D[i]=U[i]=i;
L[i+1]=i;R[i]=i+1;
}R[m]=0;
size=m+1;
memset(H,-1,sizeof(H));
memset(mark,0,sizeof(mark));
for(i=1;i<=n;i++)
{
scanf("%d",&num);
while(num--)
{
scanf("%d",&j);
Link(i,j);
}
}
flag=0;
Dance(0);
if(!flag) printf("NO\n");
}
return 0;
}