H

Problem F: Frequent values

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 Specification

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 Specification

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

RMQ问题

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <string>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <list>
#include <iomanip>
#include <cstdlib>
#include <sstream>
using namespace std;
typedef long long LL;
const int INF=0x5fffffff;
const double EXP=1e-6;
const int MS=100005;

int dp[MS][20];
int a[MS],cnt[MS];
int num[MS],l[MS],r[MS];
int n,q;

void RMQ_init()
{
    for(int i=0;i<n;i++)
        dp[i][0]=cnt[i];
    for(int j=1;(1<<j)<=n;j++)
    {
        for(int i=0;i+(1<<j)-1<n;i++)
            dp[i][j]=max(dp[i][j-1],dp[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(dp[l][k],dp[r-(1<<k)+1][k]);
}



int main()
{
    while(scanf("%d%d",&n,&q)==2&&n)
    {
        for(int i=0;i<n;i++)
            scanf("%d",&a[i]);
        a[n]=a[n-1]+1;
        int start=0;
        int id=0;
        for(int i=0;i<=n;i++)
        {
            if(i>0&&a[i]>a[i-1])
            {
                for(int j=start;j<i;j++)
                    r[j]=i-1;
                cnt[id]=i-start;
                id++;
                start=i;
            }
            l[i]=start;
            num[i]=id;
        }
        n=id;
        RMQ_init();
        int x,y;
        while(q--)
        {
            scanf("%d%d",&x,&y);
            x--;
            y--;
            int ans=0;
            if(num[x]==num[y])
            {
                printf("%d
",y-x+1);
                continue;
            }
            ans=max(r[x]-x+1,y-l[y]+1);
            if(num[x]+1<num[y])
                ans=max(ans,RMQ(num[x]+1,num[y]-1));
            printf("%d
",ans);
        }

    }
    return 0;
}