UVA 10457 - Magic Car【最小瓶颈树】

题目链接：
https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=600&problem=1398&mosmsg=Submission+received+with+ID+14106648

题意：
m条路，每条路上必须维持速度v，现在有一辆车，启动能量和结束能量为a, b，途中消耗能量为经过路径最大速度减去最小速度，现在每次循环给定起点终点，问最小能量花费

代码：

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <queue>
#include <math.h>
#include <string>

using namespace std;

const int MAXN = 410000;//点
const int MAXM = 410000;//边

struct Edge
{
    int u, v;
    int w;
    friend bool operator < (Edge a, Edge b)
    {
        return a.w < b.w;
    }
}edge[MAXM];

int f[MAXN];
int find(int x)
{
    if (f[x] == x) return x;
    else return f[x] = find(f[x]);
}

int main()
{
    int n, m, k;
    while (scanf("%d%d", &n, &m) != EOF)
    {
        int x, y, z;
        for (int i = 0; i < m; i++)
        {
            scanf("%d%d%d", &edge[i].u, &edge[i].v, &edge[i].w);
        }
        sort(edge, edge + m);
        scanf("%d%d", &x, &y); int ans = x + y;
        scanf("%d",&k);
        while (k--)
        {
            scanf("%d%d", &x, &y);
            int tmp = 1000000000;

            for (int i = 0; i < m; i++)
            {
                for (int j = 1; j <= n; j++) f[j] = j;
                for (int j = i; j < m; j++)
                {
                    int t1 = find(edge[j].u);
                    int t2 = find(edge[j].v);
                    if (t1 != t2) f[t1] = t2;
                    if (find(x) == find(y))
                    {
                        tmp = min(tmp, edge[j].w - edge[i].w);
                        break;
                    }
                }
            }
            printf("%d\n", ans + tmp);
        }
    }
    return 0;
}