UVa 11235 RMQ

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

const int maxn = 100000 + 100;
const int maxlog = 20;

int a[maxn],num[maxn],Left[maxn],Right[maxn];
int counts[maxn];
int n,q;
int segcnt;

struct RMQ
{
int d[maxn][maxlog];

void init()
{
memset(d,-0x3f,sizeof(d));

for(int i=1; i<=segcnt; i++)
d[i][0] = counts[i];

for(int j=1; (1<<j)<=segcnt; j++)
for(int k=1; k+(1<<(j-1)) <= segcnt; k++)
d[k][j] = max(d[k][j-1],d[k+(1<<(j-1))][j-1]);
}

int query(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]);
}

}solver;

int main()
{
//freopen("E:\\acm\\input.txt","r",stdin);
while(cin>>n && n)
{
cin>>q;

for(int i=1; i<=n; i++)
scanf("%d",&a[i]);

segcnt = 0;
for(int i=1; i<=n; i++)
{
num[i] = ++segcnt;
Left[i] = i;
counts[segcnt] = 1;

for(int j=i+1; j<=n+1; j++)
{
if(j == n+1)
{
i = n+1;
break;
}
if(a[j] != a[i])
{
for(int k=i; k<j; k++)
Right[k] = j-1;
i = j-1;
break;
}
counts[segcnt]++;
Left[j] = i;
num[j] = segcnt;
}
}

solver.init();
while(q--)
{
int l,r;
scanf("%d %d",&l,&r);
if(num[l] == num[r]) printf("%d\n",r-l+1);
else
{
int ans = max(Right[l]-l+1,r-Left[r]+1);
if(num[l]+1 < num[r])
{
ans = max(ans,solver.query(num[l]+1,num[r]-1));
}
printf("%d\n",ans);
}
}
}
}