delete pics to save space

2.1395.cpp

@@ -0,0 +1,54 @@
+#include<cstdio>
+#include<algorithm>
+using namespace std;
+const int maxn=100;
+struct Edge
+{
+	int a,b,v;
+};
+inline bool operator<(const Edge& a,const Edge& b)
+{
+	return a.v<b.v;
+}
+Edge e[maxn*maxn+5];
+int fa[maxn+5];
+const int oo=1<<30;
+int ff(int n)
+{
+	int a=n,b;
+	while(n!=fa[n]) n=fa[n];
+	while(a!=n)
+	{
+		b=fa[a];
+		fa[a]=n;
+		a=b;
+	}
+	return n;
+}
+int n,m,res,L,R,cnt;
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	while(scanf("%d%d",&n,&m)==2&&n)
+	{
+		for(int i=0;i<m;i++) scanf("%d%d%d",&e[i].a,&e[i].b,&e[i].v);
+		sort(e,e+m);
+		res=oo;
+		for(L=0;L<m;L++)
+		{
+			for(int i=1;i<=n;i++) fa[i]=i;
+			cnt=n;
+			for(R=L;cnt>1&&R<m;R++)
+				if(ff(e[R].a)!=ff(e[R].b))
+				{
+					fa[ff(e[R].b)]=ff(e[R].a);
+					cnt--;
+				}
+			if(cnt==1) res=min(res,e[R-1].v-e[L].v);
+		}
+		printf("%d\n",res==oo?-1:res);
+	}
+	return 0;
+}