bzoj1579 [Usaco2009 Feb]Revamping Trails 道路升级(分层图最短路)

#include <bits/stdc++.h>
using namespace std;
#define pa pair<int,pair<int,int> >
#define ll long long
#define inf 1LL<<60
#define N 10010
#define M 50010
inline int read(){
int x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-') f=-1;ch=getchar();}
while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();
return x*f;
}
int n,m,k,h
,num=0;
bool f
[22];
ll d
[22],ans=inf;
struct edge{
int to,next,val;
}data[M<<1];
void Dijkstra(){
priority_queue<pa,vector<pa>,greater<pa> >q;
for(int i=1;i<=n;++i)
for(int j=0;j<=k;++j) d[i][j]=inf;
q.push(make_pair(0,make_pair(1,0)));d[1][0]=0;
while(!q.empty()){
int x=q.top().second.first,kx=q.top().second.second;
q.pop();if(f[x][kx]) continue;f[x][kx]=1;
for(int i=h[x];i;i=data[i].next){
int y=data[i].to;
if(d[x][kx]+data[i].val<d[y][kx]){
d[y][kx]=d[x][kx]+data[i].val;
q.push(make_pair(d[y][kx],make_pair(y,kx)));
}
if(kx+1<=k&&d[x][kx]&l
112e3
t;d[y][kx+1]){
d[y][kx+1]=d[x][kx];
q.push(make_pair(d[y][kx+1],make_pair(y,kx+1)));
}
}
}
}
int main(){
//  freopen("a.in","r",stdin);
n=read();m=read();k=read();
while(m--){
int x=read(),y=read(),v=read();
data[++num].to=y;data[num].next=h[x];h[x]=num;data[num].val=v;
data[++num].to=x;data[num].next=h[y];h[y]=num;data[num].val=v;
}
Dijkstra();
for(int i=0;i<=k;++i) ans=min(ans,d
[i]);
printf("%lld\n",ans);
return 0;
}