Magical Girl Haze(分层最短路）

Magical Girl Haze

注意这个是单向的，搞了半天，没看懂英文

#include<bits/stdc++.h>
#define ll long long
#define INF 0x7f7f7f7f
using namespace std;
const int M=6*1000000+10;
int head[M],cnt;
int vis[M];
ll dis[M];
int n,m,k;
struct node
{
    int v;
    ll w;
    int nxt;
} edge[M];
void add(int x,int y,ll w)
{
    edge[++cnt].nxt=head[x];
    edge[cnt].v=y;
    edge[cnt].w=w;
    head[x]=cnt;
}
struct mul
{
    int id;
    ll w;
    friend bool operator <(mul x,mul y)
    {
        return x.w>y.w;
    }
};
void Dijkstra(int x)
{
    mul now;
    memset(vis,0,sizeof(vis));
    memset(dis,INF,sizeof(dis));
    dis[x]=0;
    priority_queue<mul>qu;
    //priority_queue<pair<int,int>,vector<pair<int,int> >,greater<pair<int,int> > > qu;
    now.id=x;
    now.w=0;
    qu.push(now);
    //qu.push(make_pair(0,x));
    while(!qu.empty( ))
    {
        //int u=qu.top( ).second;
        now=qu.top( );
        int u=now.id;
        qu.pop( );
        if(!vis[u])
        {
            vis[u]=1;
            for(int i=head[u]; i!=-1; i=edge[i].nxt)
            {
                int v=edge[i].v;
                if(dis[v]>edge[i].w+dis[u])
                {
                    dis[v]=edge[i].w+dis[u];
                    now.id=v;
                    now.w=dis[v];
                    qu.push(now);
                    //qu.push(make_pair(dis[v],v));
                }
            }
        }
    }
}
int main( )
{
    int t,x,y;
    ll w;
    scanf("%d",&t);
    while(t--)
    {
        memset(head,-1,sizeof(head));
        cnt=0;
        scanf("%d%d%d",&n,&m,&k);
        for(int i=1; i<=m; i++)
        {
            scanf("%d%d%lld",&x,&y,&w);
            for(int j=0; j<=k; j++)
            {
                add(x+j*n,y+j*n,w);
                //add(y+j*n,x+j*n,w);
            }
            for(int j=1; j<=k; j++)
            {
                add(x+(j-1)*n,y+j*n,0);
                //add(y+(j-1)*n,x+j*n,0);
            }
        }
        Dijkstra(1);
        ll ans=INF;
        //cout<<INF<<endl;
        for(int i=0; i<=k; i++)
        {
            ans=min(ans,dis[n+i*n]);
        }
        printf("%lld\n",ans);
    }
    return 0;
}