LightOJ 1221 - Travel Company(SPFA判负环)

比较简单：

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#include <iostream>#include <queue>#include <stack>using namespace std;const int M = 9999;const int N = 109;const int INF = 0x3f3f3f3f;struct LT{    int to,nex,val;}L[M];int F[N],cnt;void add(int f,int t,int d){    L[cnt].to = t;    L[cnt].nex = F[f];    L[cnt].val = d;    F[f] = cnt++;}int n,m,p,dis[N],inque[N],con[N];int que[N*N];void solve(){    memset(dis,0,sizeof(dis));    memset(con,0,sizeof(con));    for(int i=0;i<n;i++) que[i]=i,inque[i] = 1;    int fin = 0;    int front=0,rear =n;    while(rear>front)    {        int e =que[front++];        con[e]++;        if(con[e]>=n)        {            fin = true;            break;        }        inque[e] = 0;        for(int i=F[e];i;i=L[i].nex)        {            int to =L[i].to;            if(dis[to]>dis[e]+L[i].val)            {                dis[to] = dis[e]+L[i].val;                if(!inque[to])                {                    inque[to] = true;                    if(con[to]>(n>>1)&&front>0)                    que[--front]=to;                    else que[rear++] = to;                }            }        }    }    if(fin) printf("YES\n");    else printf("NO\n");}int main(){    freopen("in.txt","r",stdin);    int cas,T=1;    scanf("%d",&cas);    while(cas--)    {        scanf("%d%d%d",&n,&m,&p);        memset(F,0,sizeof(F));cnt=1;        int a,b,c,d;        for(int i=0;i<m;i++)        {            scanf("%d%d%d%d",&a,&b,&c,&d);            add(a,b,d*p-c);        }        printf("Case %d: ",T++);        solve();    }    return 0;}