hdu1233 还是畅通工程 基础最小生成树

Posted 2020-09-29

 1 //克鲁斯卡尔
 2 #include<iostream>
 3 #include<algorithm>
 4 using namespace std;
 5 const int maxn = 10005;
 6 struct node
 7 {
 8     int begin, end, len;
 9 }cun[maxn];
10 int n, fa[maxn], ans, m;
11 
12 bool cmp(node a, node b)
13 {
14     return a.len<b.len;  //按长度有小到大排序 
15 }
16 
17 void init()
18 {
19     for (int i = 0; i <= n; i++)
20     {
21         fa[i] = i;
22     }
23 }
24 
25 int find(int x)
26 {
27     if (x == fa[x])
28         return fa[x];
29     else
30         return fa[x] = find(fa[x]);
31 }
32 
33 void join(int a, int b)
34 {
35     a = find(a);
36     b = find(b);
37     if (a != b)
38         fa[b] = a;
39 }
40 
41 int kruskal()
42 {
43     sort(cun, cun + m, cmp);
44     init();  //初始化并查集 
45     ans = 0;
46     for (int i = 0; i<m; i++)
47     {
48         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 
49         {
50             join(cun[i].begin, cun[i].end);
51             ans += cun[i].len;
52         }
53     }
54     return ans;
55 }
56 
57 int main()
58 {
59     while (cin >> n)
60     {
61         if (n == 0) break;
62         m = n*(n - 1) / 2;
63         for (int i = 0; i<m; i++)
64             cin >> cun[i].begin >> cun[i].end >> cun[i].len;
65         cout << kruskal() << endl;
66     }
67     return 0;
68 }

 

 1 //prim
 2 #include<iostream>
 3 #include<cstdio>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<algorithm>
 7 using namespace std;
 8 
 9 #define INF 0x7fffffff
10 # define MAXN 120
11 typedef long long int LL;
12 
13 LL n, m;
14 LL cmpa[MAXN][MAXN], book[MAXN], dis[MAXN];
15 
16 int main()
17 {
18     LL a, b, weight, ans, p, q, f1, f2, minn, mark;
19     while (scanf("%I64d", &n) && n)
20     {
21         //初始化 这题prime算法合适，边那摩多，都是完全图了
22         for (LL i = 0; i<MAXN; i++)
23         {
24             dis[i] = INF;
25             for (LL j = 0; j<MAXN; ++j)
26                 cmpa[i][j] = INF;
27         }
28 
29         memset(book, 0, sizeof(book));
30         ans = 0;
31 
32         for (LL i = 0; i<n*(n - 1) / 2; ++i)
33         {
34             scanf("%I64d %I64d %I64d", &a, &b, &weight);
35             cmpa[a][b] = cmpa[b][a] = weight;
36         }
37 
38         //连通图
39         book[1] = 1;
40         dis[1] = -1;
41 
42         for (LL t = 1; t<n; ++t)
43         {
44             for (LL i = 2; i <= n; ++i)
45             {//更新dis中的值 
46                 for (LL j = 1; j <= n; ++j)
47                 {
48                     if (book[j] && dis[i]>cmpa[i][j])
49                     {  //j在树中 
50                         dis[i] = cmpa[i][j];
51                     }
52                 }
53             }
54 
55             //选点建树
56             minn = INF, mark = 0;
57             for (LL i = 2; i <= n; ++i)
58             {
59                 if (book[i])
60                     continue;
61                 else
62                 {
63                     if (dis[i] < minn)
64                     {
65                         minn = dis[i];
66                         mark = i;
67                         }
68                 }
69             }
70 
71             if (minn != INF)
72             {
73                 ans += minn;
74                 book[mark] = 1;
75                 dis[mark] = -1;
76             }
77                     
78         }
79         cout << ans << endl;
80 
81     }
82     return 0;
83 }