UVA 11235 Frequent Values ---RMQ

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#include <iostream>

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

using namespace std;

#define N 100003



int a[N],num[N],le[N],ri[N],cnt[N];

int d[N][21],n,type;





void RMQ_init()

{

    int i,j;

    for(i=1;i<=type;i++)

        d[i][0] = cnt[i];

    for(j=1;(1<<j)<=type;j++)

    {

        for(i=1;i+(1<<j)-1<=type;i++)

            d[i][j] = max(d[i][j-1],d[i+(1<<(j-1))][j-1]);

    }

}



int LOG[50007];

void getLog(int n)

{

    for(int i=0;i<=n;i++)

        LOG[i] = (int)(log((double)i)/log(2.0));

}



int RMQ(int l,int r)

{

    int k = LOG[R-L+1];

    return max(d[l][k],d[r-(1<<k)+1][k]);

}



int main()

{

    int q,i,j,pos;

    int l,r;

    while(scanf("%d",&n)!=EOF && n)

    {

        scanf("%d",&q);

        for(i=1;i<=n;i++)

            scanf("%d",&a[i]);

        a[0] = -1000000;

        type = 0;

        for(pos=1;pos<=n;pos++)

        {

            if(a[pos] != a[pos-1])

            {

                if(pos != 1 )

                    cnt[type] = pos-le[pos-1];

                num[pos] = ++type;

                for(j=le[pos-1];j<=pos-1;j++)

                    ri[j] = pos-1;

                le[pos] = pos;

                if(pos == n)

                    cnt[type] = 1,ri[pos] = pos;

            }

            else

            {

                le[pos] = le[pos-1];

                num[pos] = num[pos-1];

                if(pos == n)

                {

                     cnt[type] = pos - le[pos] + 1;

                     for(j=le[pos];j<=n;j++)

                        ri[j] = n;

                }

            }

        }

        RMQ_init();

        while(q--)

        {

            scanf("%d%d",&l,&r);

            if(num[l] == num[r])

            {

                printf("%d\n",r-l+1);

                continue;

            }

            int lmax = ri[l]-l+1;

            int rmax = r-le[r]+1;

            int mmax;

            if(num[l]+1 > num[r]-1)

                mmax = 0;

            else

                mmax = RMQ(num[l]+1,num[r]-1);

            printf("%d\n",max(mmax,max(lmax,rmax)));

        }

    }

    return 0;

}

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