全局最小割
stoer_wagner
论打板选手的自我修养
1 //Achen
2 #include<algorithm>
3 #include<iostream>
4 #include<cstring>
5 #include<cstdlib>
6 #include<vector>
7 #include<cstdio>
8 #include<queue>
9 #include<cmath>
10 const int N=507,inf=0x7fffffff;
11 typedef long long LL;
12 using namespace std;
13 int n,m,eg[N][N];
14
15 template<typename T>void read(T &x) {
16 char ch=getchar(); x=0; T f=1;
17 while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();
18 if(ch=='-') f=-1,ch=getchar();
19 for(;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0'; x*=f;
20 }
21
22 int vis[N],dis[N],id[N];
23 int stoer_wagner(int n) {
24 int res=inf;
25 for(int i=0;i<n;i++) id[i]=i;
26 while(n>1) {
27 memset(vis,0,sizeof(vis));
28 memset(dis,0,sizeof(dis));
29 int pr=0;
30 vis[id[pr]]=1;
31 for(int i=1;i<n;i++) {
32 int k=-1;
33 for(int j=1;j<n;j++) if(!vis[id[j]]) {
34 dis[id[j]]+=eg[id[pr]][id[j]];
35 if(k==-1||dis[id[j]]>dis[id[k]]) k=j;
36 }
37 vis[id[k]]=1;
38 if(i==n-1) {
39 res=min(res,dis[id[k]]);
40 for(int j=0;j<n;j++) {
41 eg[id[pr]][id[j]]+=eg[id[k]][id[j]];
42 eg[id[j]][id[pr]]+=eg[id[j]][id[k]];
43 }
44 id[k]=id[--n];
45 }
46 pr=k;
47 }
48 }
49 return res;
50 }
51
52 int main() {
53 while(scanf("%d%d",&n,&m)==2) {
54 memset(eg,0,sizeof(eg));
55 for(int i=1;i<=m;i++) {
56 int x,y,z;
57 read(x); read(y); read(z);
58 eg[x][y]+=z; eg[y][x]+=z;
59 }
60 printf("%d
",stoer_wagner(n));
61 }
62 return 0;
63 }