学步园

#include<cstdio>
#include<cstring>
#include<iostream>
#define INF 0x7fffffff 
#define N 6001
#define M 1000010
using namespace std;
struct data{
	int from,to,v,c,next;
}e[M];
long long ans;
int n,k,dis[N],head[N],from[N],q[M],cnt=1;
bool inq[N];
void insert(int u,int v,int w,int c){
	e[++cnt].from=u;
	e[cnt].to=v;
	e[cnt].v=w;
	e[cnt].c=c;
	e[cnt].next=head[u];
	head[u]=cnt;
}
void ins(int u,int v,int w,int c){
	insert(u,v,w,c);
	insert(v,u,0,-c);
}
bool spfa(){
	int t=0,w=1,i,now;
	memset(dis,-1,sizeof(dis));
	q[0]=0;inq[0]=1;dis[0]=0;
	while(t<w){
		now=q[t++];i=head[now];
		while(i){
			if(e[i].v>0&&dis[now]+e[i].c>dis[e[i].to]){
				dis[e[i].to]=dis[now]+e[i].c;
				from[e[i].to]=i;
				if(!inq[e[i].to]){
					q[w++]=e[i].to;inq[e[i].to]=true;
				}
			}
			i=e[i].next;
			inq[now]=false;
		}
	}
	if(dis[6000]==-1)return false;
	else return true;
}
void mincf(){
	int i=from[6000],sum=INF;
	while(i){
		sum=min(sum,e[i].v);
		i=from[e[i].from];
	}
	i=from[6000];
	while(i){
		e[i].v-=sum;
		e[i^1].v+=sum;
		ans+=sum*e[i].c;
		i=from[e[i].from];
	}
}
int main(){
	scanf("%d %d",&n,&k);
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++){
			int x;scanf("%d",&x);
			ins((i-1)*n+j,(i-1)*n+j+n*n,1,x);
			ins((i-1)*n+j,(i-1)*n+j+n*n,k,0);
			if(j<n)ins((i-1)*n+j+n*n,(i-1)*n+j+1,k,0);
			if(i<n)ins((i-1)*n+j+n*n,i*n+j,k,0);
		}
	ins(0,1,k,0);ins(2*n*n,6000,k,0);
	while(spfa())mincf();
	printf("%lld",ans);
	return 0;
}