kruskal 最小生成树算法

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 using namespace std;
 5  
 6 const int N = 105, M = 10050;
 7 int par[N], ans, n, m, t;
 8 struct edge { int u, v, w;} e[M];
 9 bool cmp(edge a, edge b){ return a.w < b.w;}
10  
11 long long read()
12 {
13     char ch=getchar();
14     long long x=0;
15     while(ch>‘9‘ || ch<‘0‘)ch=getchar();
16     while(ch>=‘0‘ && ch<=‘9‘)x=(x<<1)+(x<<3)+(ch^‘0‘),ch=getchar();
17     return x;
18 }
19 
20 int find(int x)
21 {
22     int r = x, tmp;
23     while(par[r] >= 0) r = par[r];
24     while(x != r)
25     {
26         tmp = par[x];
27         par[x] = r;
28         x = tmp;
29     }
30     return r;
31 }
32  
33 void unio(int u, int v)
34 {
35     int ru = find(u), rv = find(v), tmp = par[ru] + par[rv];
36     if(par[ru] < par[rv])
37         par[rv] = ru, par[ru] = tmp;
38     else
39         par[ru] = rv, par[rv] = tmp;
40 }
41  
42 void kruskal()
43 {
44     int cur = 0, u, v;
45     memset(par, -1, sizeof(par));
46     for(int i = 1; i <= m; ++i)
47     {
48         u = e[i].u, v = e[i].v;
49         if(find(u) != find(v))
50         {
51             ans += e[i].w;
52             unio(u, v);
53             ++cur;
54         }
55         if(cur >= n - 1) return;
56     }
57 }
58  
59 int main()
60 {
61     while(~scanf("%d", &n))
62     {
63         ans = m = 0;
64         for(int i = 1; i <= n; ++i)
65         {
66             for(int j = 1; j <= n; ++j)
67             {
68                 t=read();
69                 if(j < i) e[++m].u = i, e[m].v = j, e[m].w = t;
70             }
71         }
72         sort(e + 1, e + m + 1, cmp);
73         kruskal();
74         printf("%d\n", ans);
75     }
76     return 0;
77 }