【poj3422】 Kaka's Matrix Travels

// poj3422
#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#include<cmath>
#include<queue>
#define LL long long
#define inf 2147483640
#define Pi acos(-1.0)
#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
using namespace std;
  
const int maxn=100010;
struct edge {int from,to,next,c,w;}e[maxn<<1];
int head[maxn],dis[maxn],vis[maxn],f[maxn],p[maxn];
int cnt=1,n,m,es,et,K;
 
void link(int u,int v,int c,int w) {
    e[++cnt]=(edge){u,v,head[u],c,w};head[u]=cnt;
    e[++cnt]=(edge){v,u,head[v],-c,0};head[v]=cnt;
}
int SPFA() {
    queue<int> q;
    memset(dis,-1,sizeof(dis));
    q.push(es);dis[es]=0;f[es]=inf;
    while (!q.empty()) {
        int x=q.front();q.pop();
        vis[x]=0;
        for (int i=head[x];i;i=e[i].next) if (e[i].w && dis[e[i].to]<dis[x]+e[i].c) {
                dis[e[i].to]=dis[x]+e[i].c;
                f[e[i].to]=min(f[x],e[i].w);
                p[e[i].to]=i;
                if (!vis[e[i].to]) q.push(e[i].to),vis[e[i].to]=1;
            }
    }
    if (dis[et]==-1) return 0;
    for (int i=p[et];i;i=p[e[i].from]) e[i].w-=f[et],e[i^1].w+=f[et];
    return f[et]*dis[et];
}
int EK() {
    int ans=0;
    for (int i=1;i<=K;i++) ans+=SPFA();
    return ans;
}  
int main() {
    scanf("%d%d",&n,&K);
    es=n*n+1;et=n*n+2;
    for (int i=1;i<=n;i++)
        for (int x,y,w,j=1;j<=n;j++) {
            scanf("%d",&w);
            x=(i-1)*n+j;y=x+n*n+2;
            link(x,y,w,1);link(x,y,0,inf);
            if (i<n) link(y,x+n,0,inf);
            if (j<n) link(y,x+1,0,inf);
        }
    link(es,1,0,inf);link(n*n+n*n+2,et,0,inf);
    printf("%d",EK());
    return 0;
}