bzoj1717

题解：

二分答案

然后ｈａｓｈ

代码：

#include<bits/stdc++.h>
using namespace std;
const int P1=,P2=,P=;
int a1[P],num[P],a2[P],flag[P],a[P],inv1[P],inv2[P],n,m;
int find(int x,int y)
{
    int k=(long long)x*y%P;
    for (;flag[k]&&(a1[k]!=x||a2[k]!=y);k=(k+)%P);
    return k;
}
int pd(int x)
{
    memset(a1,,sizeof a1);
    memset(a2,,sizeof a2);
    memset(flag,,sizeof flag);
    memset(num,,sizeof num);
    inv1[]=inv2[]=;
    for (int i=;i<=n;i++)inv1[i]=inv1[i-]*%P1,inv2[i]=inv2[i-]*%P2;
    int p1=,p2=;
    for (int i=;i<=n;i++)
     {
         p1=(p1*+a[i])%P1;
         p2=(p2*+a[i])%P2;
         if (i>x)
          {
              p1=(p1-(long long)a[i-x]*inv1[x]%P1+P1)%P1;
              p2=(p2-(long long)a[i-x]*inv2[x]%P2+P2)%P2;
          }
         if (i<x)continue;
         int l=find(p1,p2);
         a1[l]=p1;a2[l]=p2;flag[l]=;
         num[l]++;
         if (num[l]>=m)return ;
     }
    return ;
}
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=;i<=n;i++)scanf("%d",&a[i]);
    int l=,r=n;
    while (l<r)
     {
         int mid=(l+r+)/;
         if (pd(mid))l=mid;
         else r=mid-;
     }
    printf("%d\n",l);
}