【网络流24题】分配问题 代码 连接

已知有一个二分图,每个点与图另一边所有点有连边。给出边权,求最大和最小匹配。

KM裸题。但是不明白题目非要求两遍,真**无聊。

代码

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

#include<iostream>
#include<vector>
#include<cstring>
#define N 110
using namespace std;
int n,i,j;
int l[N],w[N][N],lx[N],ly[N],s[N],vx[N],vy[N];
inline int (){
int p=0; char c=getchar();
while (c<'0'||c>'9') c=getchar();
while (c>='0'&&c<='9') p=p*10+c-48,c=getchar();
return p;
}
inline int max(int a,int b){return (a>b)?a:b;}
inline bool dfs(int P){
int i=0,t=0;
vx[P]=1;
for (i=1;i<=n;i++){
if (vy[i]) continue;
t=lx[P]+ly[i]-w[P][i];
if (t==0){
vy[i]=1; if (l[i]==-1||dfs(l[i])) {l[i]=P; return true;}
} else if (s[i]>t) s[i]=t;
}
return false;
}
inline void KM(){
int i=0,j=0,x=0,d=0,ans=0;
memset(l,-1,sizeof(l)); memset(ly,0,sizeof(ly));
for (x=1;x<=n;x++){
memset(s,0x3f3f3f3f,sizeof(s));
while (1){
memset(vx,0,sizeof(vx)); memset(vy,0,sizeof(vy));
if (dfs(x)) break;
d=0x3f3f3f3f;
for (i=1;i<=n;i++) if (!vy[i]&&d>s[i]) d=s[i];
for (i=1;i<=n;i++) if (vx[i]) lx[i]-=d;
for (i=1;i<=n;i++) if (vy[i]) ly[i]+=d; else s[i]-=d;
}
}
for (i=1;i<=n;i++) if (l[i]>-1) ans+=w[l[i]][i];
if (ans<0) printf("%dn",-ans); else printf("%dn",ans);
}
int main(){
n=read();
for (i=1;i<=n;i++) lx[i]=-0x3f3f3f3f;
for (i=1;i<=n;i++)
for (j=1;j<=n;j++){
w[i][j]=-read(); lx[i]=max(lx[i],w[i][j]);
}
KM();
for (i=1;i<=n;i++) lx[i]=0;
for (i=1;i<=n;i++)
for (j=1;j<=n;j++){
w[i][j]=-w[i][j]; lx[i]=max(lx[i],w[i][j]);
}
KM();
return 0;
}

连接

COGS