UVA 1395 Slim Span(枚舉)

#include<iostream>
#include<vector>
#include<algorithm>
#include<cstring>
using namespace std;
const int maxn=100+5;
const int inf=(1<<30);
int f[maxn];
int n,m;
bool map[maxn][maxn],used[maxn];
struct edge{
    int u,v,w;
    edge(int u,int v,int w): u(u),v(v),w(w) {}
    bool operator < (const edge &rhs) const{
        return w<rhs.w;
    }
};
vector<edge> ve;
int slim;
int findset(int x) {return f[x]==x?x:f[x]=findset(f[x]);}
void kruskal(vector<edge> edges)
{
    int maxx=0,minx=inf;
    sort(edges.begin(),edges.end());
    for(int i=0;i<m;i++){
        int root1=findset(edges[i].u);
        int root2=findset(edges[i].v);
        if(root1==root2) continue;
        if(edges[i].w==inf) return;
        f[root2]=root1;
        minx=min(minx,edges[i].w);
        maxx=max(maxx,edges[i].w);
    }
    slim=min(slim,abs(maxx-minx));
}
void dfs(int u)
{
    for(int i=1;i<=n;i++){
        if(map[u][i]&&used[i]==false){
            used[i]=true;
            dfs(i);
        }
    }
}
int main()
{
    while(scanf("%d%d",&n,&m)&&(n+m))
    {
        slim=inf;
        ve.clear();
        memset(map,false,sizeof(map));
        memset(used,false,sizeof(used));
        for(int i=0;i<m;i++){
            int u,v,w;
            scanf("%d%d%d",&u,&v,&w);
            ve.push_back(edge(u,v,w));
            map[u][v]=map[v][u]=true;
        }
        sort(ve.begin(),ve.end());
        int count=0;
        used[1]=true;
        dfs(1);
        for(int i=1;i<=n;i++) if(used[i]) count++;
        if(count<n) {printf("-1\n");continue;}
        for(int i=1;i<=n;i++) f[i]=i;
        kruskal(ve);
        for(int i=0;i<m;i++){
            for(int j=1;j<=n;j++) f[j]=j;
            ve[i].w=inf;
            kruskal(ve);
        }
        printf("%d\n",slim);
    }
    return 0;
}