P2186
求强连通分量,用邻接表储存,然后缩点,统计出度的点.话说我很勇敢的使用了邻接矩阵..然后就mle了
orz的是求强连通分量我还只会kosajura..
#include
<
iostream
>
#include
<
stdio.h
>
using
namespace
std;
int
n,m;
int
t
=
0
;
const
int
MAXN
=
10001
;
const
int
MAXM
=
50001
;
bool
used[MAXN];
int
p[MAXN];
int
pos[MAXN];
int
len;
int
d[MAXN];
int
b[MAXN],bb[MAXN];
int
x_[MAXM],y_[MAXM];
struct
node
{
int v; int next;
}
ts[MAXM],tss[MAXM];
void
dfs(
int
x)
{ used[x]=true; int p_=b[x]; while(p_>0)
{ int i=ts[p_].v; if (used[i]) {p_=ts[p_].next;continue;} dfs(i); p_=ts[p_].next;
} t++; p[t]=x;}
void
dfs1(
int
x)
{ used[x]=true; int p=bb[x]; while(p>0) { int i=tss[p].v; if (used[i]) {p=tss[p].next;continue;} dfs1(i); p=tss[p].next; } pos[x]=len;}
void
insert(
int
x,
int
y,
int
i)
{ ts[i].v=y; ts[i].next=b[x]; b[x]=i; tss[i].v=x; tss[i].next=bb[y]; bb[y]=i;}
int
main()
{ memset(b,0,sizeof(b)); memset(bb,0,sizeof(bb)); scanf("%d %d",&n,&m); for (int i=1;i<=m;i++) { int x,y; scanf("%d %d",&x,&y); x_[i]=x; y_[i]=y; insert(x,y,i); } memset(used,false,sizeof(used)); for (int i=1;i<=n;i++) { if (!used[i]) { dfs(i); } } len=0; memset(used,false,sizeof(used)); for (int i=t;i>=1;i--) { int k=p[i]; if (!used[k]) { len++; dfs1(k); } } memset(d,0,sizeof(d)); for (int i=1;i<=m;i++) { int x=pos[x_[i]]; int y=pos[y_[i]]; if (x==y) continue; d[x]++; } int result=0; int max_=0; int co=0; for (int i=1;i<=len;i++) { if (d[i]==0) co++; } if (co!=1) cout<<0<<endl; else { for (int i=1;i<=len;i++) if (d[i]==0) { for (int j=1;j<=n;j++) if (pos[j]==i) result++; } cout<<result<<endl; } system("pause"); return 0;}