The Unique MST----poj1679次小生成树

题目链接：http://poj.org/problem?id=1679

判断最小生成数是否唯一：如果唯一这权值和次小生成树不同，否则相同；

#include<stdio.h>
#include<string.h>
#include<map>
#include<iostream>
#include<algorithm>
#include<math.h>
#define N 110
#define INF 0xfffffff

using namespace std;

int Max[N][N], used[N][N], vis[N], maps[N][N], dist[N], fa[N], n;

void Init()
{
    memset(vis, , sizeof(vis));
    memset(used, , sizeof(used));
    memset(Max, , sizeof(Max));
    memset(fa, , sizeof(fa));
    for(int i=; i<=n; i++)
    {
        dist[i] = INF;
        for(int j=; j<=n; j++)
            if(i == j)
                maps[i][j] = ;
            else
                maps[i][j] = INF;
    }
}

int Prim(int start)
{
    int ans=;
    for(int i=; i<=n; i++)
    {
        dist[i] = maps[start][i];
        fa[i] = start;
    }
    vis[start] = ;
    for(int i=; i<=n; i++)
    {
        int Min = INF, index = -;
        for(int j=; j<=n; j++)
        {
            if(vis[j]== && Min > dist[j])
            {
                Min = dist[j];
                index = j;
            }
        }
        if(index == -)break;
        vis[index] = ;
        ans += Min;
        used[fa[index]][index] = used[index][fa[index]] = ;
        for(int j=; j<=n; j++)
        {
            if(vis[j] ==  && index != j)
            {
                Max[index][j] = Max[j][index] = max(Max[fa[index]][j], dist[index]);
            }
            else if(vis[j] ==  && dist[j] > maps[index][j])
            {
                dist[j] = maps[index][j];
                fa[j] = index;
            }
        }
    }
    return ans;
}

int SMST(int ans)
{
    int Min = INF;
    for(int i=; i<=n;i++)
    {
        for(int j=i+; j<=n; j++)
        {
            if(used[i][j]== && maps[i][j] != INF)
                Min=min(Min, ans-Max[i][j]+maps[i][j]);
        }
    }
    return Min;
}

int main()
{
    int T, m, a, b, c;
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d%d", &n, &m);
        Init();
        for(int i=; i<m; i++)
        {
            scanf("%d%d%d", &a, &b, &c);
            maps[a][b] = maps[b][a] = c;
        }
        int num1 = Prim();
        int num2 = SMST(num1);
        if(num1 != num2)
            printf("%d\n", num1);
        else
            printf("Not Unique!\n");
    }
    return ;
}