【POJ 3368】Frequent values（RMQ）

Description

You are given a sequence of n integers a₁ , a₂ , ... , a_n in non-decreasing order. In addition to that, you are given several queries consisting of indices i and j (1 ≤ i ≤ j ≤ n). For each query, determine the most frequent value among the integers a_i , ... , a_j.

Input

The input consists of several test cases. Each test case starts with a line containing two integers n and q (1 ≤ n, q ≤ 100000). The next line contains n integers a₁ , ... , a_n (-100000 ≤ a_i ≤ 100000, for each i ∈ {1, ..., n}) separated by spaces. You can assume that for each i ∈ {1, ..., n-1}: a_i ≤ a_i+1. The following q lines contain one query each, consisting of two integers i and j (1 ≤ i ≤ j ≤ n), which indicate the boundary indices for the 
query.

The last test case is followed by a line containing a single 0.

Output

For each query, print one line with one integer: The number of occurrences of the most frequent value within the given range.

Sample Input

10 3
-1 -1 1 1 1 1 3 10 10 10
2 3
1 10
5 10
0

Sample Output

1
4
3

题意：

给出N个数和Q次询问区间[L,R]，对于每个询问，找到区间内连续出现最多次的数，输出该次数。

题解：

首先将每个数的连续出现次数存入数组f[i]，对于所询问区间内，将最左子区间的连续且相同数进行特殊处理，单独计算该数在此区间的次数，然后计算此区间内除该数外的rmq，两者取最值即可。

#include<algorithm>
#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
typedef long long ll;
const int MAX=;
int dp[MAX][],mm[MAX],f[MAX];
void initrmq(int n,int b[])
{
    mm[]=-;
    for(int i=;i<=n;i++)
    {
        mm[i]=((i&(i-))==)?mm[i-]+:mm[i-];
        dp[i][]=f[i];
    }
    for(int j=;j<=mm[n];j++)
        for(int i=;i+(<<j)-<=n;i++)
            dp[i][j]=max(dp[i][j-],dp[i+(<<(j-))][j-]);
}
int rmq(int x,int y)
{
    int k=mm[y-x+];
    return max(dp[x][k],dp[y-(<<k)+][k]);
}
int main()
{
    int n,q,i;
    while(scanf("%d",&n)&&n)
    {
        scanf("%d",&q);
        int b[MAX];
        for(i=;i<=n;i++)
        {
            scanf("%d",&b[i]);
            if(i==)
            {
                f[i]=;
                continue;
            }
            if(b[i]==b[i-])
                f[i]=f[i-]+;
            else f[i]=;
        }
        initrmq(n,f);
        for(i=;i<=q;i++)
        {
            int l,r;
            scanf("%d%d",&l,&r);
            int tl=l;
            while(tl<=r&&b[tl]==b[tl-])tl++;
            printf("%d\n",max(tl-l,rmq(tl,r)));
        }
    }
    return ;
}