HDU1054+最小顶点覆盖
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/* 最小顶点覆盖:选出最少的点,这些点的关联的边都被覆盖 最小顶点覆盖等于最大匹配 */ #include<stdio.h> #include<stdlib.h> #include<string.h> #include<iostream> #include<algorithm> #include<queue> #include<map> #include<math.h> using namespace std; const int maxn = 1505; const int inf = 0x7fffffff; struct node{ int u,val,next; }edge[ maxn<<2 ]; int head[ maxn ],vis[ maxn ],fa[ maxn ]; int cnt; void init(){ memset( head,-1,sizeof(vis) ); memset( fa,-1,sizeof(fa) ); cnt=0; } void addedge( int a,int b,int c ){ edge[ cnt ].u=b; edge[ cnt ].val=c; edge[ cnt ].next=head[ a ]; head[ a ]=cnt++; } int dfs( int x ){ // int u=head[ x ]; for( int i=head[ x ];i!=-1;i=edge[i].next ){ int u=edge[ i ].u; if( vis[ u ]==0 ){ vis[ u ]=1; if( fa[ u ]==-1 || dfs( fa[u] ) ){ fa[ u ]=x; return 1; } } } return 0; } int main(){ int n; while( scanf("%d",&n)!=EOF ){ char s[ 2001 ]; init(); for( int i=0;i<n;i++ ){ int a,b,c; int tmp; scanf("%d:(%d)",&a,&tmp); while( tmp-- ){ scanf("%d",&b); addedge( a,b,1 ); addedge( b,a,1 ); } } int ans=0; for( int i=0;i<n;i++ ){ if( head[ i ]==-1 ) continue; memset( vis,0,sizeof(vis) ); ans+=dfs( i ); } printf("%d\n",ans/2); } return 0; }
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