标签：des style blog io ar color os sp for
2 1 1 2 2 2 1 2 2 1
1777 -1
拓扑排序。。
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
typedef long long LL;
using namespace std;
#define REPF( i , a , b ) for ( int i = a ; i <= b ; ++ i )
#define REP( i , n ) for ( int i = 0 ; i < n ; ++ i )
#define CLEAR( a , x ) memset ( a , x , sizeof a )
const int maxn=10100;
int head[maxn*2],next[maxn*2],end[maxn*2];
int in[maxn],val[maxn];
int n,m,cnt,k;
void toposort()
{
int sum=0;
k=0;
queue<int>q;
REPF(i,1,n)
if(!in[i]) q.push(i);
while(!q.empty())
{
int v=q.front();
sum+=val[v];
q.pop();
k++;
for(int i=head[v];i!=-1;i=next[i])
{
if(--in[end[i]]==0)
{
q.push(end[i]);
val[end[i]]=val[v]+1;
}
}
}
if(k==n) printf("%d\n",sum);
else printf("-1\n");
}
void add(int x,int y)
{
next[cnt]=head[x];
end[cnt]=y;
head[x]=cnt++;
}
int main()
{
int x,y;
while(~scanf("%d%d",&n,&m))
{
cnt=0;
REPF(i,1,n) val[i]=888;
CLEAR(in,0);
CLEAR(head,-1);
REP(i,m)
{
scanf("%d%d",&x,&y);
add(y,x);
in[x]++;
}
toposort();
}
return 0;
}
标签：des style blog io ar color os sp for
原文地址：http://blog.csdn.net/u013582254/article/details/41734849
