UVa 11235 RMQ

代码：

#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);
            }
        }
    }
}