BZOJ 2763 分层图最短路

突然发现我不会分层图最短路，写一发。　就是同层中用双向边相连，用单向边连下一层

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <string>
#include <cstring>
#include <queue>
#include <vector>
#define pa pair<int,int>
#define mp make_pair
#define fi first
#define se second
using namespace std;
const int Maxm=5000100;
const int Maxn=1000100;
const int Inf=0x3f3f3f3f;
priority_queue<pa,vector<pa>,greater<pa> > Q;
int head[Maxn],dis[Maxn],n,m,k,S,T,u,v,w,cnt;
struct Edge{int to,next,w;}edge[Maxm];
inline void Add(int u,int v,int w)
{edge[cnt].to=v;edge[cnt].next=head[u];edge[cnt].w=w;head[u]=cnt++;}
inline void ADD(int u,int v,int w) {Add(u,v,w),Add(v,u,w);}
inline int Get(int u,int Dep) {return u+(Dep-1)*n;}

void Dij()
{
    Q.push(mp(0,Get(S,1)));
    for (int i=0;i<=Get(n,k);i++) dis[i]=Inf;
    dis[Get(S,1)]=0;
    while (!Q.empty())
    {
        int u=Q.top().se; Q.pop();
        for (int i=head[u];i!=-1;i=edge[i].next)
            if (dis[u]+edge[i].w<dis[edge[i].to])
            {
                dis[edge[i].to]=dis[u]+edge[i].w;
                Q.push(mp(dis[edge[i].to],edge[i].to));
            }
    }
}
int main()
{
    scanf("%d%d%d",&n,&m,&k); k++;
    scanf("%d%d",&S,&T); S++,T++;
    memset(head,-1,sizeof(head));
    for (int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&u,&v,&w); u++,v++;
        for (int j=1;j<=k;j++) ADD(Get(u,j),Get(v,j),w);
        for (int j=1;j<k;j++)
            Add(Get(u,j),Get(v,j+1),0),
            Add(Get(v,j),Get(u,j+1),0);
    }
    Dij();
    printf("%d
",dis[Get(T,k)]);
    return 0;
}