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）