luogu P3153 [CQOI2009]跳舞

#include<cstdio>
#include<iostream>
#include<cstring>
#include<vector>
#include<queue>
#define ri register int
#define N 505
#define INF 1000000007
#define T (4*n+1)

using namespace std;

int n,k,x;
vector<int> to,w;
vector<int> ed[N];
int cur[N],d[N];
char g[N][N];

void add_edge(int u,int v,int w1,int w2) {
  to.push_back(v); w.push_back(w1); ed[u].push_back(to.size()-1);
  to.push_back(u); w.push_back(w2); ed[v].push_back(to.size()-1);
}

bool bfs() {
  queue<int> q;
  memset(d,0x3f,sizeof(d));
  d[0]=0; q.push(0);
  while (!q.empty()) {
    int x=q.front(); q.pop();
    for (ri i=0,l=ed[x].size();i<l;i++) {
      int e=ed[x][i];
      if (w[e] && d[x]+1<d[to[e]]) {
        d[to[e]]=d[x]+1;
        q.push(to[e]);
      }
    }
  }
  return d[T]<=1000000;
}

int dfs(int x,int limit) {
  if (x==T || !limit) return limit;
  int tot=0;
  for (ri &i=cur[x];i<ed[x].size();i++) {
    int e=ed[x][i];
    if (d[to[e]]==d[x]+1 && w[e]) {
      int f=dfs(to[e],min(limit,w[e]));
      if (!f) continue;
      w[e]-=f; w[1^e]+=f; 
      tot+=f; limit-=f;
      if (!limit) return tot;
    }
  }
  return tot;
}

int dinic() {
  int ret=0;
  while (bfs()) {
    memset(cur,0,sizeof(cur));
    ret+=dfs(0,INF);
  }
  return ret;
}

inline int bl(int x) {return x;}
inline int bd(int x) {return n+x;}
inline int gd(int x) {return 2*n+x;}
inline int gl(int x) {return 3*n+x;}

bool can(int x) {
  to.clear(); w.clear();
  for (ri i=0;i<=T;i++) ed[i].clear();
  for (ri i=1;i<=n;i++) add_edge(0,bl(i),x,0);
  for (ri i=1;i<=n;i++) add_edge(bl(i),bd(i),k,0);
  for (ri i=1;i<=n;i++) add_edge(gd(i),gl(i),k,0);
  for (ri i=1;i<=n;i++) add_edge(gl(i),T,x,0);
  for (ri i=1;i<=n;i++) 
    for (ri j=1;j<=n;j++) if (g[i][j]==‘Y‘) add_edge(bl(i),gl(j),1,0); else add_edge(bd(i),gd(j),1,0);
  if (dinic()==x*n) return 1; else return 0;
}

int main() {
  scanf("%d %d",&n,&k);
  for (ri i=1;i<=n;i++) scanf("%s",g[i]+1);
  int lb=0,rb=n;
  int ans=-1;
  while (lb<=rb) {
    int mid=(lb+rb)/2;
    if (can(mid)) ans=mid,lb=mid+1; else rb=mid-1;
  }
  cout<<ans<<endl;
}