最短路之SPFA（单源）HDU 1317

#include <iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<queue>
#define N 110
#define INF 0x7ffffff
using namespace std;
int n,val[N],mp[N][N],d[N],v[N],num[N],r[N][N];
void floyd()
{
    for(int k=1;k<=n;k++)
        for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
                r[i][j]=max(r[i][j],r[i][k]&r[k][j]);
}
int spfa(int s,int t)
{
    for(int i=1;i<=n;i++)
    {
        num[i]=0;
        d[i]=-INF;
        v[i]=0;
    }
    queue<int> q;
    q.push(s);
    v[s]=1;
    d[s]=100;
    num[s]++;
    while(!q.empty())
    {
        int c=q.front();
        q.pop();
        v[c]=0;
        for(int i=1;i<=n;i++)
        {
            if(d[c]+mp[c][i]>0&&d[i]<d[c]+mp[c][i])
            {
                d[i]=d[c]+mp[c][i];
                if(!v[i])
                {
                    if(++num[i]>=n)  return r[i][t];
                    v[i]=1,q.push(i);
                }
            }
        }
    }
    if(d[t]>0) return 1;
    return 0;
}
int main()
{
    while(~scanf("%d",&n)&&n!=-1)
    {
        memset(mp,0,sizeof(mp));
        memset(r,0,sizeof(r));
        for(int i=1;i<=n;i++)
        {
            int nn;
            scanf("%d%d",&val[i],&nn);
            for(int j=0;j<nn;j++)
            {
                int c;
                scanf("%d",&c);
                mp[i][c]=1;
                r[i][c]=1;
            }
        }
        for(int i=1;i<=n;i++)
            for(int j=1;j<=n;j++)
            {
                if(mp[i][j]==0) mp[i][j]=-INF;
                else    mp[i][j]*=val[j];
            }
        floyd();
        if(spfa(1,n))   cout<<"winnable"<<endl;
        else cout<<"hopeless"<<endl;
    }
}