[bzoj4443][Scoi2015]小凸玩矩阵（二分答案+二分图最大匹配）

#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<iostream>
const int N=251;
using namespace std;
struct st{int to,next;} e[N*N];
int n,m,k,i,j,t,cnt,l,r,mid,ans,a

,b[N*N],fi
,f
;
bool vis
;
void add(int x,int y){e[++cnt].to=y; e[cnt].next=fi[x]; fi[x]=cnt;}
bool find(int x)
{
for (int i=fi[x];i;i=e[i].next)
if (!vis[e[i].to])
{
int y=e[i].to;
vis[y]=1;
if (!f[y] || find(f[y])){f[y]=x; return 1;}
}
return 0;
}

bool check(int x)
{
int num=0;
cnt=0;
for (int i=1;i<=n;i++) fi[i]=0;
for (int i=1;i<=m;i++) f[i]=0;
for (int i=1;i<=n;i++)
for (int j=1;j<=m;j++)
if (a[i][j]<=x) add(i,j);
for (int i=1;i<=n;i++)
{
for (int j=1;j<=m;j++) vis[j]=0;
if (find(i)) num++;
if (num==k) return 1;
}
return 0;
}

int main()
{
scanf("%d%d%d\n",&n,&m,&k);
k=n-k+1;
for (i=1;i<=n;i++,scanf("\n"))
for (j=1;j<=m;j++)
{
scanf("%d",&a[i][j]);
b[++t]=a[i][j];
}
sort(b+1,b+t+1);
t=unique(b+1,b+t+1)-(b+1);
for (l=1,r=t;l<=r;)
{
mid=(l+r)>>1;
if (check(b[mid])) ans=b[mid],r=mid-1;
else l=mid+1;
}
printf("%d",ans);
}