传送门：https://www.luogu.org/problem/P4568
就是一个分层图
1 #include<bits/stdc++.h> 2 using namespace std; 3 4 int n,m,k; 5 int s,t; 6 int dis[15][50009]; 7 int vis[15][50009]; 8 struct node{ 9 int numk,num,val; 10 bool operator <(const node &a)const 11 { 12 return a.val<val; 13 } 14 }; 15 struct edge{ 16 int next,to,w; 17 }e[3000009];int tot; 18 int first[50009]; 19 inline void add_edge(int a,int b,int c) 20 { 21 e[++tot].next=first[a]; 22 e[tot].to=b; 23 e[tot].w=c; 24 first[a]=tot; 25 } 26 inline int read() 27 { 28 int x=0,f=1;char ch=getchar(); 29 while(ch<'0'||ch>'9'){if(ch=='-')f=1;ch=getchar();} 30 while(ch>='0'&&ch<='9'){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();} 31 return x*f; 32 } 33 inline void dijkstra() 34 { 35 priority_queue<node>q; 36 memset(dis,0x3f3f3f3f,sizeof(dis)); 37 dis[0][s]=0; 38 q.push((node){0,s,0}); 39 while(!q.empty()) 40 { 41 node uall=q.top(); 42 int uk=uall.numk; 43 int u=uall.num; 44 q.pop(); 45 if(vis[uk][u])continue; 46 vis[uk][u]=true; 47 for(register int i=first[u];i;i=e[i].next) 48 { 49 int v=e[i].to; 50 if(uk+1<=k&&dis[uk][u]<dis[uk+1][v]) 51 { 52 dis[uk+1][v]=dis[uk][u]; 53 if(vis[uk+1][v]==false)q.push((node){uk+1,v,dis[uk+1][v]}); 54 } 55 if(dis[uk][u]+e[i].w<dis[uk][v]) 56 { 57 dis[uk][v]=dis[uk][u]+e[i].w; 58 if(vis[uk][v]==false)q.push((node){uk,v,dis[uk][v]}); 59 } 60 } 61 } 62 } 63 int main() 64 { 65 n=read(),m=read(),k=read(); 66 s=read(),t=read(); 67 for(register int i=1,a,b,c;i<=m;i++) 68 { 69 a=read(),b=read(),c=read(); 70 add_edge(a,b,c); 71 add_edge(b,a,c); 72 } 73 dijkstra(); 74 int ans=99999999; 75 for (register int i=0;i<=k;i++) 76 ans=min(ans,dis[i][t]); 77 cout<<ans; 78 }
