HDU 1317 SPFA 判正环

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SPFA它没死
Source

SPFA判正环好题
具体解释看注释：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#define fuck cout << "fuck" << endl;
#define mem(a,b) memset(a,b,sizeof(a))
#define Fast ios::sync_with_stdio(false);
const int N = 2e2 + 7;
const int INF = 0x3f3f3f3f;
using namespace std;
typedef long long ll;
struct Edge
{
    int v,w,next;
} edge[N*N];
int cnt,head[N],n;
int vis[N],d[N],num[N];
void init()
{
    cnt=0;
    mem(head,-1);
}
void addedge(int u,int v,int w)
{
    edge[cnt].v=v,edge[cnt].w=w;
    edge[cnt].next=head[u];
    head[u]=cnt++;
}
//spfa判正环
void spfa(int s)
{
    memset(vis,0,sizeof(vis));
    memset(num,0,sizeof(num));
    for(int i = 1;i <= n;++i)
    {
    	vis[i] = 0;
    	num[i] = 0;
    }
    //起点能量为100
    for(int i=1; i<=n; i++)
        d[i]=i==s?100:-INF;
    vis[s]=1;
    queue<int>que;
    que.push(s);
    while(!que.empty())
    {
        int u=que.front();
        que.pop();
        vis[u]=0;
        num[u]++;//入队次数加一
        if(num[u]>n) d[u]=INF;//如果u是正环内的点 则能量值可以为INF
        for(int i=head[u]; i!=-1; i=edge[i].next)
        {
            int v=edge[i].v,w=edge[i].w;
            if(d[u]+w>0&&d[v]<d[u]+w)//保证中途能量不为非正数
            {
                d[v]=d[u]+w;
                //如果入队次数多于n就不入队了
                //否则会死循环
                if(!vis[v]&&num[v]<=n)
                {
                    vis[v]=1;
                    que.push(v);
                }
            }
        }
    }
}
int main()
{
    int e,m,t;
    while(~scanf("%d",&n)&&n!=-1)
    {
        init();
        for(int i=1; i<=n; i++)
        {
            scanf("%d %d",&e,&m);
            while(m--)
            {
                scanf("%d",&t);
                addedge(i,t,e);
            }
        }
        spfa(1);
        //如果能走到终点且最大能量大于0
        if(d[n]>0) printf("winnable\n");
        else printf("hopeless\n");
    }
    return 0;
}