BZOJ 2763 分层图最短路

Posted 2020-07-13 yyjxx2010xyu

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

 1 #include <cstdio>
 2 #include <algorithm>
 3 #include <iostream>
 4 #include <string>
 5 #include <cstring>
 6 #include <queue>
 7 #include <vector>
 8 #define pa pair<int,int>
 9 #define mp make_pair
10 #define fi first
11 #define se second
12 using namespace std;
13 const int Maxm=5000100;
14 const int Maxn=1000100;
15 const int Inf=0x3f3f3f3f;
16 priority_queue<pa,vector<pa>,greater<pa> > Q;
17 int head[Maxn],dis[Maxn],n,m,k,S,T,u,v,w,cnt;
18 struct Edge{int to,next,w;}edge[Maxm];
19 inline void Add(int u,int v,int w)
20 {edge[cnt].to=v;edge[cnt].next=head[u];edge[cnt].w=w;head[u]=cnt++;}
21 inline void ADD(int u,int v,int w) {Add(u,v,w),Add(v,u,w);}
22 inline int Get(int u,int Dep) {return u+(Dep-1)*n;}
23 
24 void Dij()
25 {
26     Q.push(mp(0,Get(S,1)));
27     for (int i=0;i<=Get(n,k);i++) dis[i]=Inf;
28     dis[Get(S,1)]=0;
29     while (!Q.empty())
30     {
31         int u=Q.top().se; Q.pop();
32         for (int i=head[u];i!=-1;i=edge[i].next)
33             if (dis[u]+edge[i].w<dis[edge[i].to])
34             {
35                 dis[edge[i].to]=dis[u]+edge[i].w;
36                 Q.push(mp(dis[edge[i].to],edge[i].to));
37             }
38     }
39 }
40 int main()
41 {
42     scanf("%d%d%d",&n,&m,&k); k++;
43     scanf("%d%d",&S,&T); S++,T++;
44     memset(head,-1,sizeof(head));
45     for (int i=1;i<=m;i++)
46     {
47         scanf("%d%d%d",&u,&v,&w); u++,v++;
48         for (int j=1;j<=k;j++) ADD(Get(u,j),Get(v,j),w);
49         for (int j=1;j<k;j++)
50             Add(Get(u,j),Get(v,j+1),0),
51             Add(Get(v,j),Get(u,j+1),0);
52     }
53     Dij();
54     printf("%d\\n",dis[Get(T,k)]);
55     return 0;
56 }

C++