POJ 1598 find the most comfortable road

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1598

思路：通过思路转换，可以看出是求两个点之间最大边权值与最小边权值之差最小的。克鲁斯卡尔算法枚举之~

#include <iostream>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>
#include <cstdlib>
#include <string>
using namespace std;
int n,m;
int f[210];

struct node
{
    int u,v;
    int w;
}map[1020];

int getf(int a)
{
    if(f[a] == a)
        return a;
    f[a] = getf(f[a]);
    return f[a];
}

void merge(int a, int b)
{
    int x = getf(a);
    int y = getf(b);

    if(x!=y)
        f[y] = x;
}

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

bool cmp(node a, node b)
{
    return a.w < b.w;
}

int solve(int start, int end)
{
    int maxn = -1;
    int minn = 999999999;
    sort(map,map+m,cmp);
    int res = 999999999;

    for(int k = 0; k < m; k++)
    {
        init();
        maxn = -1;
        minn = 999999999;
        for(int i = k; i < m; i++)
        {
            if(getf(map[i].u) != getf(map[i].v))
            {
                merge(map[i].u, map[i].v);
                maxn = max(maxn, map[i].w);
                minn = min(minn, map[i].w);
            }
            if(getf(start) == getf(end))
            {
                res = min(maxn - minn, res);
                break;
            }
        }
    }

    if(res == 999999999)
        res = -1;
    return res;
}

int main()
{
    int q;
    while(scanf("%d %d", &n, &m)!=EOF)
    {
        for(int i=0; i<m; i++)
        {
            scanf("%d %d %d", &map[i].u, &map[i].v, &map[i].w);
        }

        scanf("%d", &q);
        int s[20][2];

        for(int i=1; i<=q; i++)
        {
            init();
            scanf("%d %d", &s[i][0], &s[i][1]);
            printf("%d\n", solve(s[i][0],s[i][1]));
        }
    }
    return 0;
}