Bzoj 2324 Rescue Pikachu

http://www.lydsy.com/JudgeOnline/problem.php?id=2324

Idea: Minimum cost maximum flow

Consider setting the array d[k][i][j], which represents the shortest path to only the first K cities, I to J

And then you can build the diagram.

S->0 flow rate is K, the cost is 0

I->i+n traffic is INF with a cost of 0

I+n->t Flow rate is 1

I+n->j traffic is INF, cost is D[J][I][J]

S->i flow rate is 1, the cost is 0 represents if a person to the I city, it can continue to walk, thereby renewing a new traffic.

1#include <algorithm>2#include <cstdio>3#include <cmath>4#include <cstring>5#include <iostream>6 #defineINF 0x7fffffff7 intd[205][205][205],a[205][205],k;8 inttot,go[200005],next[200005],first[200005],cost[200005],flow[200005];9 intop[200005],dis[200005],c[200005],vis[200005],edge[200005], from[200005];Ten intS,t,n,m,ans; One intRead () { A     CharCh=getchar ();intt=0, f=1; -      while(ch<'0'|| Ch>'9'){if(ch=='-') f=-1; ch=GetChar ();} -      while('0'<=ch&&ch<='9') {t=t*Ten+ch-'0'; ch=GetChar ();} the     returnt*F; - } - voidInsertintXintYintZintl) { -tot++; +go[tot]=y; -next[tot]=First[x]; +first[x]=tot; Aflow[tot]=Z; atcost[tot]=l; - } - voidAddintXintYintZintl) { -Insert (x,y,z,l); op[tot]=tot+1; -Insert (Y,x,0,-L); op[tot]=tot-1; - } in BOOLSPFA () { -      for(intI=0; i<=t;i++) todis[i]=0x3f3f3f3f, vis[i]=0; +     intH=1, t=1; c[1]=s;vis[s]=1;d is[s]=0; -      while(h<=t) { the         intnow=c[h++]; *          for(intI=first[now];i;i=Next[i]) { $             intPur=Go[i];Panax Notoginseng             if(dis[pur]>dis[now]+cost[i]&&Flow[i]) { -dis[pur]=dis[now]+Cost[i]; theedge[pur]=i; +                  from[pur]=Now ; A                 if(Vis[pur])Continue; thevis[pur]=1; +c[++t]=pur; -             } $         } $vis[now]=0; -     } -     returndis[t]!=0x3f3f3f3f; the } - voidUpdata () {Wuyi     intmn=0x7ffffff; the      for(intI=t;i!=s;i= from[i]) { -mn=std::min (Mn,flow[edge[i]); Wu     } -      for(intI=t;i!=s;i= from[i]) { Aboutans+=mn*Cost[edge[i]]; $flow[edge[i]]-=mn; -flow[op[edge[i]]]+=mn; -     } - } A intMain () { +N=read (); M=read (); k=read (); the      for(intI=0; i<=n;i++) -       for(intj=0; j<=n;j++) $       if(i!=j) { thea[i][j]=0x3f3f3f3f; the}Else thea[i][j]=0; the      for(intI=1; i<=m;i++){ -         intU=read (), V=read (), w=read (); ina[u][v]=std::min (a[u][v],w); thea[v][u]=std::min (a[v][u],w); the     } About      for(intk=0; k<=n;k++){ the          for(intI=0; i<=n;i++) the           for(intj=0; j<=n;j++) theA[i][j]=std::min (a[i][k]+a[k][j],a[i][j]); +          for(intI=0; i<=n;i++) -           for(intj=0; j<=n;j++) thed[k][i][j]=A[i][j]; Bayi     } thes=2*n+2; t=s+1; theAdd (S,0K0); -      for(intI=0; i<=n;i++) -Add (i,i+n+1Inf0); the      for(intI=0; i<=n;i++) theAdd (I,t,1,0); the      for(intI=0; i<=n;i++) theAdd (s,i+n+1,1,0); -      for(intI=0; i<=n;i++) the       for(intj=i+1; j<=n;j++) the       if(d[j][i][j]<0x3f3f3f3f) theAdd (i+n+1, J,inf,d[j][i][j]);94      while(SPFA ()) Updata (); theprintf"%d\n", ans);  the}

Bzoj 2324 Rescue Pikachu