UVA 11235 Frequent values

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

const int INF=0x7FFFFFFF;
const int maxn=100000+10;
int a[maxn];
int Value[maxn],Count[maxn];
int num[maxn],left[maxn],right[maxn];
int N,Q,tot;
int Max[maxn][32];

void init()
{
tot=0;
a[0]=-INF;
memset(Count,0,sizeof Count);
a[N+1]=-INF;
memset(num,-1,sizeof num);
memset(left,-1,sizeof left);
memset(right,-1,sizeof right);
}

void init_RMQ()
{
memset(Max,0,sizeof Max);
for(int i=1; i<=tot; i++) Max[i][0] = Count[i];
for(int j=1; (1<<j)<=tot; j++)
{
for(int i=1; i+(1<<j)<=tot; i++)
{
Max[i][j] = max(Max[i][j-1], Max[i+(1<<(j-1))][j-1]);
}
}
}

int Query(int L, int R)
{
if(L > R) return 0;
int k = 0;
while((1<<(1+k)) <= R-L+1) k++;
return max(Max[L][k], Max[R-(1<<k)+1][k]);
}

int main()
{
while(~scanf("%d",&N))
{
if(N==0) break;
scanf("%d",&Q);
init();
for(int i=1; i<=N; i++) scanf("%d",&a[i]);
for(int i=1; i<=N; i++)
{
if(a[i]!=a[i-1])
{
tot++;
Value[tot]=a[i];
}
Count[tot]++;
}

init_RMQ();

int id=0,P;
for(int i=1; i<=N; i++)
{
if(num[i]==-1)
{
id++;
for(int j=i; j<=N+1; j++)
{
if(a[j]!=a[i])
{
P=j-1;
break;
}
}
for(int j=i; j<=P; j++)
{
num[j]=id;
left[j]=i;
right[j]=P;
}
}
}

for(int i=1; i<=Q; i++)
{
int LL,RR;
scanf("%d%d",&LL,&RR);
if(num[LL]==num[RR]) printf("%d\n",RR-LL+1);
else
{
int ans;
ans=max((right[LL]-LL+1),(RR-left[RR]+1));
if(num[LL]+1<=num[RR]-1) ans=max(ans,(Query(num[LL]+1,num[RR]-1)));
printf("%d\n",ans);
}
}
}
return 0;
}