hdu1233 还是畅通工程 基础最小生成树

 //克鲁斯卡尔
 #include<iostream>
 #include<algorithm>
 using namespace std;
 const int maxn = ;
 struct node
 {
     int begin, end, len;
 }cun[maxn];
 int n, fa[maxn], ans, m;

 bool cmp(node a, node b)
 {
     return a.len<b.len;  //按长度有小到大排序
 }

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

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

 void join(int a, int b)
 {
     a = find(a);
     b = find(b);
     if (a != b)
         fa[b] = a;
 }

 int kruskal()
 {
     sort(cun, cun + m, cmp);
     init();  //初始化并查集
     ans = ;
     for (int i = ; i<m; i++)
     {
         if (find(cun[i].begin) != find(cun[i].end)) //一条边的两个端点不在同一个集合，则选他，并合并
         {
             join(cun[i].begin, cun[i].end);
             ans += cun[i].len;
         }
     }
     return ans;
 }

 int main()
 {
     while (cin >> n)
     {
         if (n == ) break;
         m = n*(n - ) / ;
         for (int i = ; i<m; i++)
             cin >> cun[i].begin >> cun[i].end >> cun[i].len;
         cout << kruskal() << endl;
     }
     return ;
 }

 //prim
 #include<iostream>
 #include<cstdio>
 #include<cstdlib>
 #include<cstring>
 #include<algorithm>
 using namespace std;

 #define INF 0x7fffffff
 # define MAXN
 typedef long long int LL;

 LL n, m;
 LL cmpa[MAXN][MAXN], book[MAXN], dis[MAXN];

 int main()
 {
     LL a, b, weight, ans, p, q, f1, f2, minn, mark;
     while (scanf("%I64d", &n) && n)
     {
         //初始化 这题prime算法合适，边那摩多，都是完全图了
         for (LL i = ; i<MAXN; i++)
         {
             dis[i] = INF;
             for (LL j = ; j<MAXN; ++j)
                 cmpa[i][j] = INF;
         }

         memset(book, , sizeof(book));
         ans = ;

         for (LL i = ; i<n*(n - ) / ; ++i)
         {
             scanf("%I64d %I64d %I64d", &a, &b, &weight);
             cmpa[a][b] = cmpa[b][a] = weight;
         }

         //连通图
         book[] = ;
         dis[] = -;

         for (LL t = ; t<n; ++t)
         {
             for (LL i = ; i <= n; ++i)
             {//更新dis中的值
                 for (LL j = ; j <= n; ++j)
                 {
                     if (book[j] && dis[i]>cmpa[i][j])
                     {  //j在树中
                         dis[i] = cmpa[i][j];
                     }
                 }
             }

             //选点建树
             minn = INF, mark = ;
             for (LL i = ; i <= n; ++i)
             {
                 if (book[i])
                     continue;
                 else
                 {
                     if (dis[i] < minn)
                     {
                         minn = dis[i];
                         mark = i;
                         }
                 }
             }

             if (minn != INF)
             {
                 ans += minn;
                 book[mark] = ;
                 dis[mark] = -;
             }

         }
         cout << ans << endl;

     }
     return ;
 }