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uva 10462

這題的題目敘述寫的還真幽默
次小生成樹~

[sourcecode language="cpp"]
//============================================================================
// Name : Is There A Second Way Left.cpp
// Date : 2013 2013/2/19 上午6:37:42
// Author : GCA
//============================================================================
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
typedef long long ll;
typedef unsigned int uint;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
printf("%d ",dp[htx][hty]);}Pln();}
#define M 305
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
int tmp=min(x,y);
return min(tmp,z);
}
int max3(int x,int y,int z){
int tmp=max(x,y);
return max(tmp,z);
}
int n,e;
int p[M],rank[M],used_edge[M];
struct edge{
int x,y,w;
}edges[M];
int getf(int i){
if(i!=p[i])p[i]=getf(p[i]);
return p[i];
}
void _union(int x,int y){
if(rank[x]>rank[y])p[y]=x;
else{
p[x]=y;
if(rank[x]==rank[y])rank[y]++;
}
}
bool cmp(edge a,edge b){
return a.w<b.w;
}
int kruscal(){
for(int i=0;i<=n;i++)p[i]=i;
Set(rank,0);
int ans=0;

int k=1;
for(int i=0;i<e;i++){
if(used_edge[i])continue;
int x=edges[i].x,y=edges[i].y;
x=getf(x);y=getf(y);
if(x!=y){
k++;
_union(x,y);
used_edge[i]=1;
ans+=edges[i].w;
}
// printf("<< k %d\n",k);
}
// Pln();
if(k!=n)ans=-1;
return ans;
}
void solve(){
int save[M],tmp,mincost=oo;
tmp=kruscal();
if(tmp==-1){
printf("No way\n");
return;
}

memcpy(save,used_edge,sizeof(save));
for(int i=0;i<e;i++){
if(save[i]){
Set(used_edge,0);
used_edge[i]=1;
tmp=kruscal();
if(tmp==-1){
tmp=oo;
}
mincost=min(mincost,tmp);
}
}
if(mincost==oo)printf("No second way\n");
else printf("%d\n",mincost);

}
int main() {
ios_base::sync_with_stdio(0);
int test;
scanf("%d",&test);
int ff=0;
while(test--){
scanf("%d%d",&n,&e);
for(int i=0;i<e;i++){
scanf("%d%d%d",&edges[i].x,&edges[i].y,&edges[i].w);
}
Set(used_edge,0);
printf("Case #%d : ",++ff);
sort(edges,edges+e,cmp);
solve();
}

}

[/sourcecode]