最小生成树MST

Kruskal算法思想：贪心选边，用并查集维护点集。

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <algorithm>
 4 #include <cstring>
 5 #include <cmath>
 6 using namespace std;
 7 const int maxn = 5000 + 10;
 8 int n, m, f[maxn], sum = 0, tot = 0;
 9 struct Edge{
10     int from, to, w;
11     bool operator < (const Edge& ths) const {
12         return w < ths.w;
13     }
14 }adj[maxn];
15 int findset(int x){
16     return x == f[x] ? x : f[x] = findset(f[x]);
17 }
18 void Kruskal(){
19     sort(adj, adj + m);
20     for(int i = 0; i < m; i ++){
21         int f1 = findset(adj[i].from), f2 = findset(adj[i].to);
22         if(f1 != f2){
23             f[f2] = f1;
24             sum += adj[i].w;
25             tot ++;
26             if(tot == m) break;
27         }
28     }
29     return ;
30 }
31 void read(int &x){
32     x = 0; int sig = 1; char ch = getchar();
33     while(!isdigit(ch)) { if(ch == ‘-‘) sig = -1; ch = getchar(); }
34     while(isdigit(ch)) x = 10 * x + ch - ‘0‘, ch = getchar();
35     x *= sig; return ;
36 }
37 void init(){
38     read(n); m = n * (n - 1) * 0.5;
39     for(int i = 0; i < n; i ++) f[i] = i;
40     for(int i = 0; i < m; i ++)
41         read(adj[i].from), read(adj[i].to), read(adj[i].w);
42     return ;
43 }
44 void work(){
45     Kruskal();
46     return ;
47 }
48 void print(){
49     printf("%d\n", sum);
50     return ;
51 }
52 int main(){
53     init();
54     work();
55     print();
56     return 0;
57 }