先占坑，日后来补

贴个代码

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>

using namespace std;

const int N = 1e5 + 10;
int a[N];
int val[N], cnt[N], num[N], le[N], ri[N];
int d[N][20];
int n, q, now;

void RMQ_init(){
	for(int i = 1; i <= now; i++) d[i][0] = cnt[i];
	for(int j = 1; (1 << j) <= now; j++) //这步是保证2^j <= n  
		for(int i = 1; i + (1 << j) - 1 <= now; i++)
			d[i][j] = max(d[i][j - 1], d[i + (1 << (j - 1))][j - 1]);
}

int RMQ_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]);
}

void process(){
	memset(cnt, 0, (n + 5) * sizeof(int));
	now = 1;
	val[1] = a[1]; cnt[1] = 1; num[1] = 1; le[1] = 1; ri[1] = 1;
	
	int i = 2;
	while(a[i] == val[now]){
		cnt[1]++;
		num[i] = 1;
		le[i] = 1;
		i++;
	}
	for(int k = 1; k <= i - 1; k++) ri[k] = i - 1;
	
	for(; i <= n; i++){
		
		val[++now] = a[i];
		
		int j = i;
		while(a[j] == val[now]){
			cnt[now]++;
			num[j] = now;
			le[j] = i;
			j++;
		}
		for(int k = i; k <= j - 1; k++) ri[k] = j - 1;
		i = j - 1;	
	}
	
	RMQ_init();
}

int solve(int l, int r){
	if(num[l] == num[r]) return r - l + 1;
	
	int ans = ri[l] - l + 1;
	ans = max(ans, r - le[r] + 1);
	if(num[l] + 1 <= num[r] - 1) ans = max(ans, RMQ_query(num[l] + 1, num[r] - 1));
	
	return ans;
}

int main()
{
	while(~scanf("%d", &n) && n > 0){
		scanf("%d", &q);
		
		for(int i = 1; i <= n; i++) scanf("%d", &a[i]);
		
		process();
		
		while(q--){
			int l, r;
			scanf("%d%d", &l, &r);
			
			printf("%d\n", solve(l, r));
		}
	}
	return 0;
}