思路：裸的分层图最短路

提交：1次

题解：

如思路

代码：

#include
    
     #include
     
      #include
      
       #include
       
        #define R register intusing namespace std;#define ull unsigned long long#define ll long long#define pause (for(R i=1;i<=10000000000;++i))#define IN freopen("NOIPAK++.in","r",stdin)#define OUT freopen("out.out","w",stdout)namespace Fread {    static char B[1<<15],*S=B,*D=B;#ifndef JACK    #define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)#endif    inline int g() {        R ret=0,fix=1; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-1:fix;        if(ch==EOF) return EOF; do ret=ret*10+(ch^48); while(isdigit(ch=getchar())); return ret*fix;    } inline bool isempty(const char& ch) {return ch!=EOF&&(ch<=36||ch>=127);}    inline void gs(char* s) {        register char ch; while(isempty(ch=getchar())); if(ch==EOF) return ;        do *s++=ch; while(!isempty(ch=getchar()));    }}using Fread::g; using Fread::gs;const int N=10010,M=50010;#define fr first#define sc second#define mp make_pair#define pii pair
        
          int n,m,k,s,t,cnt,ans=0x3f3f3f3f;int vr[M<<1],nxt[M<<1],fir[N],w[M<<1],d[N][15]; bool vis[N][15];inline void add(int u,int v,int ww) {vr[++cnt]=v,nxt[cnt]=fir[u],w[cnt]=ww,fir[u]=cnt; }inline void dijk() { priority_queue
         
          
            > q; memset(d,0x3f,sizeof(d)); d[s][0]=0; q.push(mp(0,mp(s,0))); while(q.size()) { register pii tmp=q.top().sc; q.pop(); R u=tmp.fr,t=tmp.sc; if(vis[u][t]) continue; for(R i=fir[u];i;i=nxt[i]) { R v=vr[i]; if(d[v][t]>d[u][t]+w[i]) d[v][t]=d[u][t]+w[i],q.push(mp(-d[v][t],mp(v,t))); if(t
           
            d[u][t]) d[v][t+1]=d[u][t],q.push(mp(-d[v][t+1],mp(v,t+1))); } }}signed main() {#ifdef JACK#endif n=g(),m=g(),k=g(),s=g(),t=g(); for(R i=1,u,v,w;i<=m;++i) u=g(),v=g(),w=g(),add(u,v,w),add(v,u,w); dijk(); for(R i=0;i<=k;++i) ans=min(ans,d[t][i]); printf("%d\n",ans);}
           
          
         
        
       
      
     
    

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2019.07.22