Bzoj 1061 Volunteer Recruitment

http://www.lydsy.com/JudgeOnline/problem.php?id=1061

Idea: You can use the conversion of inequalities into the cost stream.

The inequality is listed, if there is a negative constant, then from the equation to the T, if it is positive from the s to the equation, the flow is constant, the cost is 0.

If it is a variable, then find the two equations of this variable, from the negative to the positive flow of the INF edge, if there is a cost, then add the cost.

1#include <cstdio>2#include <cmath>3#include <algorithm>4#include <cstring>5#include <iostream>6 #defineINF 0x7fffffff7 inttot,go[200005],next[200005],first[200005],flow[200005],cost[200005];8 intop[200005],a[200005];9 intc[200005],vis[200005],dis[200005];Ten ints,t,n,m,edge[200005], from[200005],ans; One intRead () { A     intt=0, f=1;CharCh=GetChar (); -      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=s;i<=t;i++) vis[i]=0, dis[i]=0x7fffffff; to     intH=1, t=1; vis[s]=1;d is[s]=0; +      while(h<=t) { -         intnow=c[h++]; the          for(intI=first[now];i;i=Next[i]) { *               intPur=Go[i]; $               if(flow[i]&&dis[pur]>dis[now]+Cost[i]) {Panax Notoginsengedge[pur]=i; -                   from[pur]=Now ; thedis[pur]=dis[now]+Cost[i]; +                  if(Vis[pur])Continue; Avis[pur]=1; thec[++t]=pur; +                 } -         } $vis[now]=0; $     } -     returndis[t]!=0x7fffffff; - } the voidUpdata () { -     intmn=0x7fffffff;Wuyi      for(intI=t;i!=s;i= from[i]) { themn=std::min (Mn,flow[edge[i]); -     } Wu      for(intI=t;i!=s;i= from[i]) { -ans+=mn*Cost[edge[i]]; Aboutflow[edge[i]]-=mn; $flow[op[edge[i]]]+=mn; -     } - } - intMain () { AN=read (); m=read (); +s=0; t=n+2; the      for(intI=1; i<=n;i++) a[i]=read (); -      for(intI=1; i<=m;i++){ $          intU=read (), V=read (), c=read (); theAdd (u,v+1, inf,c); the     }     the      for(intI=1; i<=n+1; i++){ the          inttmp=a[i]-a[i-1]; -          if(tmp>=0) Add (S,i,tmp,0); in          ElseAdd (I,t,-tmp,0); the          if(i>1) Add (i,i-1Inf0); the     } About      while(SPFA ()) Updata (); theprintf"%d\n", ans); the}

Bzoj 1061 Volunteer Recruitment