Frequent values

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <vector>
#include <string>
#include <cctype>
#include <complex>
#include <cassert>
#include <utility>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
using namespace std;
typedef pair<int,int> PII;
typedef long long ll;
#define lson l,m,rt<<1
#define pi acos(-1.0)
#define rson m+1,r,rt<<11
#define All 1,N,1
#define N 100010
#define read freopen("in.txt", "r", stdin)
const ll  INFll = 0x3f3f3f3f3f3f3f3fLL;
const int INF= 0x7ffffff;
const int mod =  1000000007;
int n,q,v[N],num[N],id[N],lef[N],righ[N],len,d[N][20];
void init(){
    for(int i=0;i<len;++i)
        d[i][0]=num[i];
    for(int j=1;(1<<j)<=len;++j)
        for(int i=0;i+(1<<j)-1<n;++i)
        d[i][j]=max(d[i][j-1],d[i+(1<<(j-1))][j-1]);
}
int RMQ(int l,int r){
    int k=0;
    while((1<<(k+1))<=r-l+1)k++;
    return max(d[l][k],d[r-(1<<k)+1][k]);
}
int main()
{
    int a[N];
    while(~scanf("%d",&n)&&n){
            scanf("%d",&q);
            memset(num,0,sizeof(num));
        len=0;
            scanf("%d",&a[0]);
        num[0]=1;
        id[0]=len;
        for(int i=1;i<n;++i){
            scanf("%d",&a[i]);
            if(a[i]!=a[i-1]){len++;
            }
            num[len]++;
            id[i]=len;
        }
          len++;
        lef[0]=0;
        int l=0;
        for(int i=1;i<n;++i){
            if(a[i]!=a[i-1])
            l=i;
            lef[i]=l;
        }
        int r=n-1;
        righ[r]=r;
        for(int i=n-2;i>=0;--i)
        {
            if(a[i]!=a[i+1])
                r=i;
            righ[i]=r;
        }
        init();
        int x,y;
        while(q--){
            scanf("%d%d",&x,&y);
            x--;
            y--;
            if(id[x]==id[y])
                printf("%d\n",y-x+1);
            else if(id[y]-id[x]==1)
                printf("%d\n",max(righ[x]-x+1,y-lef[y]+1));
            else
            printf("%d\n",max(max(righ[x]-x+1,y-lef[y]+1),RMQ(id[x]+1,id[y]-1)));
        }
    }
return 0;
}