bzoj3390 [Usaco2004 Dec]Bad Cowtractors牛的报复(最大生成树)

最大生成树，和最小基本一样。

#include <bits/stdc++.h>using namespace std;#define ll long long#define inf 0x3f3f3f3f#define N 20010inline int read(){    int x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9') x=x*10+ch-'0',ch=getchar();    return x*f;}int n,m,fa[1010],tot=0,ans=0;struct edge{    int x,y,val;}data[N];inline bool cmp(edge x,edge y){    return x.val>y.val;}inline int find(int x){return x==fa[x]?x:fa[x]=find(fa[x]);}int main(){//  freopen("a.in","r",stdin);    n=read();m=read();    for(int i=1;i<=n;++i) fa[i]=i;    for(int i=1;i<=m;++i) data[i].x=read(),data[i].y=read(),data[i].val=read();    sort(data+1,data+m+1,cmp);    for(int i=1;i<=m;++i){        int xx=find(data[i].x),yy=find(data[i].y);        if(xx!=yy){            fa[xx]=yy;ans+=data[i].val;tot++;        }    }    if(tot!=n-1) puts("-1");    else printf("%d\n",ans);    return 0;}