P1546 最短网络 Agri-Net

4
0 4 9 21
4 0 8 17
9 8 0 16
21 17 16 0

28

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<cmath>
 5 #include<algorithm>
 6 using namespace std;
 7 const int MAXN=4001;
 8 void read(int & n)
 9 {
10     char c='+';int x=0;
11     while(c<'0'||c>'9')c=getchar();
12     while(c>='0'&&c<='9')
13     x=x*10+(c-48),c=getchar();
14     n=x;
15 }
16 struct node
17 {
18     int u,v,w,nxt;
19 }edge[MAXN*5];
20 int head[MAXN];
21 int num=1;
22 void add_edge(int x,int y,int z)
23 {
24     edge[num].u=x;
25     edge[num].v=y;
26     edge[num].w=z;
27     edge[num].nxt=head[x];
28     head[x]=num++;
29 }
30 int fa[MAXN*6];
31 int n;
32 inline int comp(const node &a ,const node & b)
33 {
34     return a.w<b.w;
35 }
36 inline int find(int x)
37 {
38     if(fa[x]!=x)
39     return fa[x]=find(fa[x]);
40     return fa[x];
41 }
42 inline void unionn(int x,int y)
43 {
44     int fx=find(x);
45     int fy=find(y);
46     fa[fx]=fy;
47 }
48 inline void kruskal()
49 {
50     int tot=0;
51     int ans=0;
52     sort(edge+1,edge+num,comp);
53     for(int i=1;i<=num-1;i++)
54     {
55         int now=edge[i].u;int will=edge[i].v;
56         if(find(now)!=find(will))
57         {
58             unionn(now,will);
59             tot++;
60             ans+=edge[i].w;
61         }
62         if(tot==n-1)
63         break;
64     }
65     printf("%d",ans);
66 }
67 int main()
68 {
69     //freopen("agrinet.in","r",stdin);
70     //freopen("agrinet.out","w",stdout);
71     read(n);
72     for(int i=0;i<=n;i++)
73         fa[i]=i;
74     for(int i=1;i<=n;i++)
75         for(int j=1;j<=n;j++)
76         {
77             int x;
78             read(x);
79             if(x!=0)
80             add_edge(i,j,x);
81         }
82     kruskal();
83     return 0;
84 }