poj-3041 Asteroids (binary graph max match + Hungarian algorithm)

http://poj.org/problem?id=3041

There are K asteroids in the N*n grid, where the asteroid I is (RI,CI), and now there is a powerful weapon that can blast a whole row or a whole array of asteroids to ashes with a luminous speed, and to use this weapon to destroy all asteroids requires at least a few luminous beams.

Mainly the composition, will each line into a point, constitute a set of 1, each column also as a point, the composition of the set 2, each obstacle position coordinates will set 1 and set 2 points together, that is, each obstacle as the edge of the connection node, so that the subject is a minimum point coverage problem = The maximum match of the binary graph.

Can be solved by the Hungarian algorithm.

The adjacency table implements 0MS.

1#include <iostream>2#include <cstring>3#include <cstdio>4 using namespacestd;5 classedge{6  Public:7     intV,nex;8 };9Edge e[10001];Ten intn,m,k,head[10001]; One intlink[501]; A BOOLvis[501]; -  - voidInit () the { -k=0; -Memset (Head,0,sizeof(head)); - } + voidAddedge (intBinta) -{//The algorithm to add edges to the graph, note that the forward edge is added//the subsequent nodes of B are both a---->b +e[k].v=A; Ae[k].nex=Head[b]; athead[b]=k;k++; - } - BOOLDfsintu) { -      for(inti = Head[u]; I! =0; i =E[i].nex) { -         intv =e[i].v; -         if(!Vis[v]) { inVIS[V] =true; -             if(Link[v] = =-1||DFS (Link[v])) { toLINK[V] =u; +                 return true; -             } the         } *     } $     return false;Panax Notoginseng } - intMain () the { +     intu,v; Ascanf"%d%d",&n,&m); the init (); +      for(intI=0; i<m;i++) -     { $scanf"%d%d",&u,&v); $Addedge (V-1, U-1); -     } -     intans=0; thememset (link,-1,sizeof(link)); -      for(inti =0; I < n; i + +){Wuyimemset (Vis,0,sizeof(Vis)); the         if(Dfs (i)) ans++; -     } Wuprintf"%d\n", ans); -     return 0; About}

Adjacency Matrix:

1#include <cstdio>2#include <cstring>3 Const intmaxn=501;4 intUN,VN;//Number of U,v5 intG[MAXN][MAXN];//the number is 0~n-1.6 intLINKER[MAXN];7 BOOLUSED[MAXN];8 BOOLDfsintu)9 {Ten     intv; One      for(v=0; v<un;v++) A         if(g[u][v]&&!Used[v]) -         { -used[v]=true; the             if(linker[v]==-1||DFS (Linker[v])) -             { -linker[v]=u; -                 return true; +             } -         } +     return false; A } at intHungary () - { -     intres=0; -     intu; -memset (linker,-1,sizeof(linker)); -      for(u=0; u<un;u++) in     { -memset (Used,0,sizeof(used)); to         if(Dfs (U)) res++; +     } -     returnRes; the } *  $ intMain ()Panax Notoginseng { -     intu,v; thescanf"%d%d",&un,&VN); +Memset (G,0,sizeof(g)); A      while(vn--) the     { +scanf"%d%d",&u,&v); -g[u-1][v-1]=1; $     } $printf"%d\n", Hungary ()); -     return 0; -  the}

poj-3041 Asteroids (binary graph max match + Hungarian algorithm)