每日一题 day41 打卡
Analysis
分层图最短路模板
各层内部正常连边，各层之间从上到下连权值为0的边。每向下跑一层，就相当于免费搭一次飞机。跑一遍从s到t+n*k的最短路即可。
三倍经验 洛谷 P4822 [BJWC2012]冻结，洛谷 P1948 [USACO08JAN]电话线Telephone Lines，洛谷 P2939 [USACO09FEB]改造路Revamping Trails
1 #include<iostream>
2 #include<cstdio>
3 #include<cstring>
4 #include<algorithm>
5 #include<queue>
6 #define maxn 4200000+10
7 #define INF 9187201950435737471
8 #define rep(i,s,e) for(register int i=s;i<=e;++i)
9 #define dwn(i,s,e) for(register int i=s;i>=e;--i)
10 using namespace std;
11 inline int read()
12 {
13 int x=0;
14 bool f=1;
15 char c=getchar();
16 for(; !isdigit(c); c=getchar()) if(c=='-') f=0;
17 for(; isdigit(c); c=getchar()) x=(x<<3)+(x<<1)+c-'0';
18 if(f) return x;
19 return 0-x;
20 }
21 inline void write(int x)
22 {
23 if(x<0){putchar('-');x=-x;}
24 if(x>9)write(x/10);
25 putchar(x%10+'0');
26 }
27 int n,m,k,cnt,ans,s,t;
28 int head[maxn],book[maxn],dis[maxn];
29 struct node
30 {
31 int v,w,nex;
32 }edge[maxn];
33 bool cmp(int x,int y)
34 {
35 return x>y;
36 }
37 inline void add(int x,int y,int z)
38 {
39 edge[++cnt].v=y;
40 edge[cnt].w=z;
41 edge[cnt].nex=head[x];
42 head[x]=cnt;
43 }
44 void dijkstra(int s)
45 {
46 priority_queue<pair<int,int> > q;
47 memset(book,0,sizeof(book));
48 memset(dis,127,sizeof(dis));
49 dis[s]=0;
50 q.push(make_pair(0,s));
51 while(!q.empty())
52 {
53 int from=q.top().second;
54 q.pop();
55 if(book[from]==1) continue;
56 book[from]=0;
57 for(int i=head[from];i;i=edge[i].nex)
58 {
59 int to=edge[i].v,val=edge[i].w;
60 if(dis[to]>dis[from]+val)
61 {
62 dis[to]=dis[from]+val;
63 q.push(make_pair(-dis[to],to));
64 }
65 }
66 }
67 }
68 signed main()
69 {
70 n=read();m=read();k=read();
71 s=read();t=read();
72 rep(i,1,m)
73 {
74 int x=read(),y=read(),z=read();
75 add(x,y,z);
76 add(y,x,z);
77 rep(j,1,k)
78 {
79 add(j*n+x,j*n+y,z);
80 add(j*n+y,j*n+x,z);
81 add((j-1)*n+x,j*n+y,0);
82 add((j-1)*n+y,j*n+x,0);
83 }
84 }
85 dijkstra(s);
86 int temp=t;
87 int ans=dis[temp];
88 rep(i,1,k) ans=min(ans,dis[i*n+temp]);
89 write(ans);
90 return 0;
91 }
请各位大佬斧正（反正我不认识斧正是什么意思）