hdu1598 find the most comfortable road 枚举+最小生成树

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #define MAXN 210
 #define INF 2147483646
 using namespace std;

 int f[MAXN], Rank[MAXN];    //Rank长度
 int n, m, pos;

 struct Edge{
     int u, v, val;
     //按照val从小到大排列
     friend bool operator<(const Edge&a, const Edge&b){
         return a.val < b.val;
     }
 }arr[MAXN*MAXN];

 void init(){
     for (int i = ; i<MAXN; ++i)
         f[i] = i, Rank[i] = ;
 }

 int find(int x){
     int i, j = x;
     while (j != f[j]) j = f[j];
     while (x != j){
         i = f[x]; f[x] = j; x = i;
     }
     return j;
 }

 void Union(int x, int y){
     int a = find(x), b = find(y);
     if (a == b)return;
     if (Rank[a]>Rank[b])
         f[b] = a;
     else{
         if (Rank[a] == Rank[b])
             ++Rank[b];
         f[a] = b;
     }
 }

 int main(){
     int u, v, speed, Q;
     while (scanf("%d%d", &n, &m) != EOF){
         for (int i = ; i<m; ++i)
             scanf("%d%d%d", &arr[i].u, &arr[i].v, &arr[i].val);
         sort(arr, arr + m);
         scanf("%d", &Q);
         while (Q--){
             scanf("%d%d", &u, &v);
             int ans = INF;
             for (int j = ; j < m; ++j){
                 init();
                 for (int k = j; k < m; ++k){
                     Union(arr[k].u, arr[k].v);
                     if (find(u) == find(v)){
                         ans = min(ans, arr[k].val - arr[j].val);    //使ans尽可能的小
                         break;
                     }
                 }
             }
             if (ans == INF)
                 printf("-1\n");
             else
                 printf("%d\n", ans);
         }
     }
     //system("pause");
     return ;
 }