[枚举最小瓶颈生成树]UVa-1395 - Slim Span(kruskal)

就是紫书的思路，像暴力

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 105;
const int INF = 0x3f3f3f3f;
struct Edge{
    int u,v,cost;
    bool operator < (const Edge& a)const {
        return cost > a.cost;
    }
};
vector<Edge> edges;
int n,m;
int F[MAXN];
int find_(int x){
    return x==F[x]?x:F[x]=find_(F[x]);
}
int kruskal(int k){
    for(int i=0;i<=n;i++) F[i]=i;
    int cnt=0;
    int minn=INF,maxn=0;
    for(int i=k;i<m;i++){
        Edge e=edges[i];
        int v=e.v;
        int u=e.u;
        int fu=find_(u);
        int fv=find_(v);
        if(fu!=fv){
            cnt++;
            F[fu]=fv;
            minn = min(e.cost,minn);
            maxn = max(e.cost,maxn);
        }
    }
    if(cnt!=n-1) return -1;
    else return maxn-minn;
}
int main()
{
    while(~scanf("%d%d",&n,&m)){
        if(n==0&&m==0) break;
        edges.clear();
        for(int i=1;i<=m;i++){
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            edges.push_back((Edge){a,b,c});
        }
        sort(edges.begin(),edges.end());
        int ans=INF;
        for(int i=0;i<=m;i++){
            int t=kruskal(i);
            if(t==-1) break;
            ans = min(ans,t);
        }
        if(ans == INF) printf("%d\n",-1);
        else printf("%d\n",ans);
    }
    return 0;
}