lg3567[简单的主席树]

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<cstring>
#include<algorithm>
#define rep(i,x,y) for(register int i=x;i<=y;++i)
#define repd(i,x,y) for(register int i=x;i>=y;--i)
#define ll long long
using namespace std;
const int N=5e5;
int tr[N<<5],lson[N<<5],rson[N<<5],rt[N],cnt,n,m;
inline void (int &o,int l,int r,int x){
	tr[++cnt]=tr[o];lson[cnt]=lson[o];rson[cnt]=rson[o];
	o=cnt;tr[o]++;
	if(l==r)return ;
	int mid=l+r>>1;
	if(x<=mid)update(lson[o],l,mid,x);
	else update(rson[o],mid+1,r,x);
}
inline int query(int i,int j,int l,int r,int x){
	if(l==r)return l;
	int mid=l+r>>1;
	if(2*(tr[lson[j]]-tr[lson[i]])>x)return query(lson[i],lson[j],l,mid,x);
	if(2*(tr[rson[j]]-tr[rson[i]])>x)return query(rson[i],rson[j],mid+1,r,x);
	return 0;
}
int main(){
	scanf("%d%d",&n,&m);
	rep(i,1,n){int x;rt[i]=rt[i-1];scanf("%d",&x);update(rt[i],1,n,x);}
	rep(i,1,m){int l,r;scanf("%d%d",&l,&r);printf("%dn",query(rt[l-1],rt[r],1,n,r-l+1));}
	return 0;
}