2018-南京网络赛icpc-L题（分层最短路）

　　　　for(int i=1;i<=m;i++)
        {
            scanf("%lld%lld%lld",&x,&y,&w);
            for(int j=0;j<=k;j++)
            {
                add(x+j*n,y+j*n,w);同一层次的点；
                if(j!=k)
                add(x+j*n,y+(j+1)*n,0);不同层次的点，可以向它能连接的下一个层次连一个边权为0；
            }
        }
完整代码：

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#include<queue>
#include<stack>
#define ll long long
using namespace std;
const int maxm=3000500;
const ll inf=0x7f7f7f7f;
const int maxn=100500;
struct node
{
ll num;
ll dist;
node(ll _num,ll _dist):num(_num),dist(_dist){}
friend bool operator<(node a,node b)
{
return a.dist>b.dist;
}
};
struct Edge
{
ll next;
ll to;
ll w;
}edge[maxm*2];
int head[maxm];
ll dist[maxm];
int cnt;
int n,m,k;
void add(ll u,ll v,ll w)
{
edge[cnt].next=head[u];
edge[cnt].to=v;
edge[cnt].w=w;
head[u]=cnt++;
}
void dij(int u)
{
priority_queue<node>q;
memset(dist,inf,sizeof(dist));
dist[u]=0;
q.push(node(u,dist[u]));
while(!q.empty())
{
node now=q.top();
//cout<<now.num<<" "<<now.dist<<endl;
q.pop();
int x=now.num;
for(int i=head[x];i!=-1;i=edge[i].next)
{
int v=edge[i].to;
if(dist[v]>dist[x]+edge[i].w)
{
dist[v]=dist[x]+edge[i].w;
q.push(node(v,dist[v]));
}
}
}
}
int main()
{
int tt;
ll x,y,w;
scanf("%d",&tt);
while(tt--)
{
memset(head,-1,sizeof(head));cnt=0;
scanf("%d%d%d",&n,&m,&k);
if(k>=m)
{
printf("0\n");
continue;
}
for(int i=1;i<=m;i++)
{
scanf("%lld%lld%lld",&x,&y,&w);
for(int j=0;j<=k;j++)
{
add(x+j*n,y+j*n,w);
if(j!=k)
add(x+j*n,y+(j+1)*n,0);
}
}
dij(1);
ll ans=inf;
for(int i=0;i<=k;i++)
{
ans=min(ans,dist[n+i*n]);
}
printf("%lld\n",ans);
}
}