BZOJ2795: [Poi2012]A Horrible Poem

#include<set>
#include<map>
#include<deque>
#include<queue>
#include<stack>
#include<cmath>
#include<ctime>
#include<bitset>
#include<string>
#include<vector>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<climits>
#include<complex>
#include<iostream>
#include<algorithm>
#define ll long long
#define lowbit(x) x&(-x)
using namespace std;

void read(int &x)
{
char c;
while(!((c=getchar())>='0'&&c<='9'));
x=c-'0';
while((c=getchar())>='0'&&c<='9') x=(x<<3)+(x<<1)+c-'0';
}
void down(int &x,int y){if(x>y)x=y;}
const int maxn = 510000;

int gcd(int a,int b){return a==0?b:gcd(b%a,a);}

ll hk=233,hk2=1e9+7;
char s[maxn];
ll sum[maxn],pw[maxn];
int num[maxn][26];
int n,q;

bool judge(int l1,int r1,int l2,int r2)
{
ll s1=sum[r1]-sum[l1-1]*pw[r1-l1+1];
ll s2=sum[r2]-sum[l2-1]*pw[r1-l1+1];
return s1==s2;
}

int main()
{
read(n); scanf("%s",s+1);
for(int i=1;i<=n;i++)
{
for(int j=0;j<26;j++) num[i][j]=num[i-1][j]+(s[i]-j=='a');
}
for(int i=1;i<=n;i++)
sum[i]=sum[i-1]*hk+(ll)s[i];
pw[0]=1ll; for(int i=1;i<=n;i++) pw[i]=pw[i-1]*hk;

read(q);
while(q--)
{
int l,r; read(l); read(r);
int lr=(r-l+1);
int D=lr;
for(int i=0;i<26;i++)
D=gcd(D,num[r][i]-num[l-1][i]);

int ans=lr;
int k=sqrt(D);
for(int i=1;i<=k;i++)
if(D%i==0)
{
int tk;
tk=lr/i;
if(judge(l,r-tk,l+tk,r)) down(ans,tk);

if(i*i==D) break;
tk=lr/(D/i);
if(judge(l,r-tk,l+tk,r)) down(ans,tk);
}
printf("%d\n",ans);
}

return 0;
}