POJ 1679 The Unique MST 次小生成树

2
3 3
1 2 1
2 3 2
3 1 3
4 4
1 2 2
2 3 2
3 4 2
4 1 2

3
Not Unique!

#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <iostream>
#include <sstream>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <fstream>
#include <numeric>
#include <iomanip>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <ctime>

using namespace std;

#define PB push_back
#define MP make_pair
#define CLR(vis) memset(vis,0,sizeof(vis))
#define MST(vis,pos) memset(vis,pos,sizeof(vis))
#define MAX3(a,b,c) max(a,max(b,c))
#define MAX4(a,b,c,d) max(max(a,b),max(c,d))
#define MIN3(a,b,c) min(a,min(b,c))
#define MIN4(a,b,c,d) min(min(a,b),min(c,d))
#define PI acos(-1.0)
#define INF 0x7FFFFFFF
#define LINF 1000000000000000000LL
#define eps 1e-8

typedef long long ll;
typedef unsigned long long ull;

const int maxn=111;
int father[maxn];

void build(int n)
{
    for(int i=1;i<=n;i++)
        father[i]=i;
}

int find(int x)
{
    if(father[x]!= x)
	father[x]=find(father[x]);
	return father[x];
}

void merge(int x,int y)
{
	int xx=find(x);
	int yy=find(y);
	father[xx]=yy;
}

const int maxm=maxn*maxn;

struct edge{
    int u,v;
    int w;
    bool select;
}e[maxm];

bool cmp(edge A,edge B)
{
    if(A.w!=B.w) return A.w<B.w;
    if(A.u!=B.u) return A.u<B.u;
    return A.v<B.v;
}

struct node{
    int to;
    int next;
}link[maxn];

int il;
int head[maxn];
int end[maxn];
int len[maxn][maxn];

void kruskal(edge * e,int n,int m)
{
    int k=0;
    int i,x,y;
    int w,v;
    for(il=0;il<n;il++)
    {
        link[il].to=il+1;
        link[il].next=head[il+1];
        end[il+1]=il;
        head[il+1]=il;
    }
    sort(e+1,e+1+m,cmp);
    for(i=1;i<=m;i++)
    {
        if(k==n-1)
            break;
        if(e[i].w<0)
            continue;
        x=find(e[i].u);
        y=find(e[i].v);
        if(x!=y)
        {
            for(w=head[x];~w;w=link[w].next)
            {
                for(v=head[y];~v;v=link[v].next)
                {
                    len[link[w].to][link[v].to]=len[link[v].to][link[w].to]=e[i].w;
                }
            }
            link[end[y]].next=head[x];
            end[y]=end[x];
            merge(x,y);
            k++;
            e[i].select=true;
        }
    }
}

int main()
{
    int t;
    int n,m;
    int u,v,w;
    cin>>t;
    while(t--)
    {
        scanf("%d%d",&n,&m);
        build(n);
        MST(head,-1);
        for(int i=1;i<=m;i++)
        {
            scanf("%d%d%d",&u,&v,&w);
            e[i].u=u;
            e[i].v=v;
            e[i].w=w;
            e[i].select=false;
        }
        int mst,secmst;
        kruskal(e,n,m);
        mst=0;
        for(int i=1;i<=m;i++)
        {
            if(e[i].select)
                mst+=e[i].w;
        }
        secmst=INF;
        for(int i=1;i<=m;i++)
        {
            if(!e[i].select)
                secmst=min(secmst,mst+e[i].w-len[e[i].u][e[i].v]);
        }
        if(mst==secmst)
           printf("Not Unique!\n");
        else
           printf("%d\n",mst);
    }

    return 0;
}