ORZ：http://www.cnblogs.com/zrts/p/bzoj3714.html
1 #include<cstdio> 2 #include<algorithm> 3 using namespace std; 4 #define N 2010 5 int fa[N],rank[N],n,m,tot; 6 long long ans; 7 struct Edge{int u,v,w;}edges[(N*N)>>1]; 8 bool operator < (const Edge &a,const Edge &b){return a.w<b.w;} 9 void init(){for(int i=1;i<=n;i++)fa[i]=i;} 10 int Res;char C; 11 inline int R() 12 { 13 Res=0;C='*'; 14 while(C<'0'||C>'9')C=getchar(); 15 while(C>='0'&&C<='9'){Res=Res*10+(C-'0');C=getchar();} 16 return Res; 17 } 18 int findroot(int x) 19 { 20 if(x==fa[x]) return x; 21 int rt=findroot(fa[x]); 22 fa[x]=rt; 23 return rt; 24 } 25 inline void Union(const int &U,const int &V) 26 { 27 if(rank[U]<rank[V]) fa[U]=V; 28 else 29 { 30 fa[V]=U; 31 if(rank[U]==rank[V]) rank[U]++; 32 } 33 } 34 int main() 35 { 36 n=R(); init(); 37 for(int i=1;i<=n;i++) 38 for(int j=i;j<=n;j++) 39 edges[++m]=(Edge){i-1,j,R()}; 40 sort(edges+1,edges+m+1); 41 for(int i=1;i<=m;i++) 42 { 43 int f1=findroot(edges[i].u),f2=findroot(edges[i].v); 44 if(f1!=f2) 45 { 46 Union(f1,f2); 47 ans+=(long long)edges[i].w; 48 tot++; 49 if(tot==n) break; 50 } 51 } 52 printf("%lld ",ans); 53 return 0; 54 }