Cogs 14. [Network flow 24 questions] paired with pilots

This problem is actually very good thinking, because divided into positive, deputy pilots. So the pilot as a boy, the copilot as a girl. Then do hungry can.

1#include <bits/stdc++.h>2 using namespacestd;3 intg[131][131],vis[131],girl[131],n,n1;4 intHungry (intBoy )5 {6     inti;7      for(i=n1+1; i<=n;i++)8     {9         if(g[boy][i]==1&&vis[i]==0)Ten         { Onevis[i]=1; A             if(Hungry (girl[i]) = =1|| girl[i]==0) -             { -girl[i]=Boy ; the                 return 1; -             } -         } -     } +     return 0; - } + intMain () A { at     inta,b,sum,i; -scanf"%d%d",&n,&N1); -      while(SCANF ("%d%d", &a,&b)!=eof) g[a][b]=1; -Memset (Girl,0,sizeof(Girl)); -sum=0; -      for(i=1; i<=n1;i++) in     { -memset (Vis,0,sizeof(Vis)); to         if(Hungry (i) = =1) sum++; +     } -printf"%d", sum);  the     return 0; *}

View Code But this problem is "network flow 24 questions", so still want to practice a network flow. So the maximum flow can be done directly with Dinic.

1#include <cstdio>2#include <cstring>3#include <cmath>4#include <cstdlib>5#include <algorithm>6 using namespacestd;7 intn,s,t,q[131],dis[131],g[131][131];8 intMin (intAaaintBBB) {if(AAA&GT;BBB)returnbbbElse returnAAA;}9 intBfs ()Ten { One     inthead,tail,u,v; Amemset (Q,0,sizeof(q)), head=0, tail=1, q[tail]=s; -memset (dis,-1,sizeof(dis)), dis[s]=0; -      while(head<=tail) the     { -u=q[++Head]; -          for(v=1; v<=n;v++) -         { +             if(g[u][v]>0&&dis[v]<0) -             { +dis[v]=dis[u]+1; Aq[++tail]=v; at             } -         } -     } -     if(dis[n]<=0)return 0; -     Else return 1; - } in intDfs (intUintMinflow) - { to     intV,ans; +     if(u==n)returnMinflow; -      for(v=1; v<=n;v++) the     { *         if(g[u][v]>0&&dis[v]==dis[u]+1) $         {Panax Notoginsengans=Dfs (V,min (minflow,g[u][v)); -             if(ans!=0) the             { +g[u][v]-=ans; Ag[v][u]+=ans; the                 returnans; +             } -         }  $     } $     return 0; - } - intdinic () the { -     intmaxflow=0, ans;Wuyi      while(BFS ()! =0) the     { -Ans=dfs (s),0x7fffffff);if(ans==0) Break; maxflow+=ans; Wu     } -     returnMaxflow; About } $ intMain () - { -     intn1,a,b,i; -scanf"%d%d",&n,&N1); A      while(SCANF ("%d%d", &a,&b)!=eof) g[a][b]=1; +n+=2; s=n-1; t=N; the      for(i=1; i<=n1;i++) g[s][i]=1; -      for(i=n1+1; i<=n-2; i++) g[i][t]=1; $printf"%d", Dinic ()); the     return 0;  the}

View Code

Cogs 14. [Network flow 24 questions] paired with pilots