[Luogu] 逛公园

https://www.luogu.org/problemnew/show/P3953

https://www.zybuluo.com/wsndy-xx/note/1134388

#include<cstdio>
#include<cstring>
#include<cctype>
 
using namespace std;
const int N=1e5+,K=;
 
int n,m,k,p,tot,ans=;
int first[N],next[N<<],en[N<<],w[N<<];
int first1[N*K],next1[N*K<<],en1[N*K<<],d[N*K];
int q[N<<],dis[N],dis1[N],u[N<<],v[N<<],t[N<<],f[N*K];
bool bz[N];
 
inline int read() {
    int X=,w=;
    char ch=;
    while(!isdigit(ch)) {
        if(ch=='-') w=-;
        ch=getchar();
    }
    while(isdigit(ch)) X=(X<<)+(X<<)+ch-'',ch=getchar();
    return X*w;
}
 
inline void insert(int x,int y,int z) {
    next[++tot]=first[x];
    first[x]=tot;
    en[tot]=y;
    w[tot]=z;
}
 
inline void insert1(int x,int y) {
    next1[++tot]=first1[x];
    first1[x]=tot;
    en1[tot]=y;
    d[y]++;
}
 
inline int get(int x,int y) {
    return (x-)*(k+)+y+;
}
 
int main() {
    int T=read();
    while(T--) {
        n=read(),m=read(),k=read(),p=read();
        memset(first,tot=,sizeof(first));
        for(int i=; i<=m; i++) {
            u[i]=read(),v[i]=read(),t[i]=read();
            insert(u[i],v[i],t[i]);
        }
        memset(dis,,sizeof(dis));
        int l=dis[]=,r=q[]=;
        while(l<r) {
            int x=q[++l];
            bz[x]=false;
            for(int i=first[x]; i; i=next[i])
                if(dis[x]+w[i]<dis[en[i]]) {
                    dis[en[i]]=dis[x]+w[i];
                    if(!bz[en[i]]) bz[q[++r]=en[i]]=true;
                }
        }
        memset(first,tot=,sizeof(first));
        for(int i=; i<=m; i++) insert(v[i],u[i],t[i]);
        memset(dis1,,sizeof(dis1));
        l=dis1[q[r=]=n]=;
        while(l<r) {
            int x=q[++l];
            bz[x]=false;
            for(int i=first[x]; i; i=next[i])
                if(dis1[x]+w[i]<dis1[en[i]]) {
                    dis1[en[i]]=dis1[x]+w[i];
                    if(!bz[en[i]]) bz[q[++r]=en[i]]=true;
                }
        }
        memset(first1,tot=,sizeof(first1));
        memset(d,,sizeof(d));
        for(int i=; i<=m; i++) {
            int x=get(u[i],),y=get(v[i],dis[u[i]]+t[i]-dis[v[i]]);
            for(int j=dis[u[i]]; j+t[i]+dis1[v[i]]<=dis[n]+k; j++,x++,y++) insert1(x,y);
        }
        int num=(k+)*n,sum=;
        l=r=ans=;
        memset(f,,sizeof(f));
        for(int i=; i<=num; i++)
            if(!d[i]) q[++r]=i;
        f[]=;
        while(l<r) {
            int x=q[++l];
            sum++;
            for(int i=first1[x]; i; i=next1[i]) {
                if(!--d[en1[i]]) q[++r]=en1[i];
                f[en1[i]]+=f[x];
                f[en1[i]]=f[en1[i]]>p?f[en1[i]]-p:f[en1[i]];
            }
        }
        if(sum<num) printf("-1\n");
        else {
            for(int i=; i<=k; i++) ans=(ans+f[get(n,i)])%p;
            printf("%d\n",ans);
        }
    }
    return ;
}