学步园

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;
}