poj 1743 Musical Theme

#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#define N 20010  
using namespace std;
int n,p,q=1,k,a[N],rk[2][N],sa[2][N],v[N],h[N],ans=-1,f[N][16];
char s[N]; 
void mul(int *sa,int *rk,int *SA,int *RK)
{
    for(int i=1;i<=n;i++) v[rk[sa[i]]]=i;
    for(int i=n;i;i--) if(sa[i]>k) SA[v[rk[sa[i]-k]]--]=sa[i]-k;
    for(int i=n-k+1;i<=n;i++) SA[v[rk[i]]--]=i;
    for(int i=1;i<=n;i++) RK[SA[i]]=RK[SA[i-1]]+(rk[SA[i]]!=rk[SA[i-1]]||rk[SA[i]+k]!=rk[SA[i-1]+k]); 
} 
void presa()
{
    for(int i=1;i<=n;i++) v[a[i]]++;
    for(int i=1;i<=180;i++) v[i]+=v[i-1];
    for(int i=1;i<=n;i++) sa[p][v[a[i]]--]=i;
    for(int i=1;i<=n;i++) rk[p][sa[p][i]]=rk[p][sa[p][i-1]]+(a[sa[p][i]]!=a[sa[p][i-1]]);
    for(k=1;k<n;k<<=1,swap(p,q)) 
    {
        mul(sa[p],rk[p],sa[q],rk[q]);
        if(rk[q][sa[q][n]]==n) 
        {
            swap(p,q);
            return;
        }
    }
}
void getheight()
{
    int j,g=0;
    for(int i=1;i<=n;i++)
    {
        j=sa[p][rk[p][i]-1];
        while(a[i+g]==a[j+g]) g++;
        h[rk[p][i]]=g;if(g) g--;
    }
}
void pre()
{
    p=0;q=1;k=0;
    memset(a,0,sizeof(a));
    memset(rk,0,sizeof(rk));
    memset(sa,0,sizeof(sa));
    memset(v,0,sizeof(v));
    memset(h,0,sizeof(h));
    ans=-1;
}
bool check(int mid)
{
    int minn=n+1,maxn=-1;
    for(int i=2;i<=n;i++)
    {
        if(h[i]<mid)
        {
            if(maxn-minn>=mid) return true;
            minn=n+1;maxn=-1;
        }
        minn=min(minn,sa[p][i]);
        maxn=max(maxn,sa[p][i]);
    }
    if(maxn-minn>=mid) return true;
    return false;
}
void solve()
{
    int l=4,r=n,mid;
    while(l<=r)
    {
        mid=l+r>>1;
        if(check(mid)) ans=mid,l=mid+1;
        else r=mid-1;
    }
    printf("%d\n",ans+1);
}
int main()
{
    while(scanf("%d",&n))
    {
        if(!n) return 0;
        pre();
        int last,x;
        scanf("%d",&last);
        for(int i=2;i<=n;i++)
        {
            scanf("%d",&x);
            a[i-1]=x-last;
            a[i-1]+=88;
            last=x;
        }
        n--;
        presa();
        getheight();
        solve();
    }
}