【kruscal】【最小生成树】【并查集扩展】bzoj3714 [PA2014]Kuglarz

ORZ：http://www.cnblogs.com/zrts/p/bzoj3714.html

 #include<cstdio>
 #include<algorithm>
 using namespace std;
 #define N 2010
 int fa[N],rank[N],n,m,tot;
 long long ans;
 struct Edge{int u,v,w;}edges[(N*N)>>];
 bool operator < (const Edge &a,const Edge &b){return a.w<b.w;}
 void init(){for(int i=;i<=n;i++)fa[i]=i;}
 int Res;char C;
 inline int R()
 {
     Res=;C='*';
     while(C<''||C>'')C=getchar();
     while(C>=''&&C<=''){Res=Res*+(C-'');C=getchar();}
     return Res;
 }
 int findroot(int x)
 {
     if(x==fa[x]) return x;
     int rt=findroot(fa[x]);
     fa[x]=rt;
     return rt;
 }
 inline void Union(const int &U,const int &V)
 {
     if(rank[U]<rank[V]) fa[U]=V;
     else
       {
           fa[V]=U;
           if(rank[U]==rank[V]) rank[U]++;
       }
 }
 int main()
 {
     n=R(); init();
     for(int i=;i<=n;i++)
       for(int j=i;j<=n;j++)
         edges[++m]=(Edge){i-,j,R()};
     sort(edges+,edges+m+);
     for(int i=;i<=m;i++)
       {
           int f1=findroot(edges[i].u),f2=findroot(edges[i].v);
           if(f1!=f2)
             {
                 Union(f1,f2);
                 ans+=(long long)edges[i].w;
                 tot++;
                 if(tot==n) break;
             }
       }
     printf("%lld\n",ans);
     return ;
 }