competitive/dquery.cpp at main · krishna-mathuria/competitive · GitHub

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#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define BLOCK 174


struct query
{
    int l,r,ind;
}Q[200010];
int ans[200010];
int a[30010];
int cnt[1000010];
int answer;
void add(int index)
{
    cnt[a[index]]++;
    if(cnt[a[index]]==1) answer++;
}

void remove(int index)
{
    cnt[a[index]]--;
    if(cnt[a[index]]==0) answer--;
}

bool cmp(query f,query s)
{
    if((f.l/BLOCK)!=(s.l/BLOCK))
        return (f.l/BLOCK)<(s.l/BLOCK);
    else
        return f.r<s.r;
}
int main(){
    ios_base::sync_with_stdio(false);
    int n,q;
    scanf("%d",&n);
    for (int i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
    }
    scanf("%d",&q);
    for (int i=0;i<q;i++)
    {
        scanf("%d%d",&Q[i].l,&Q[i].r);
        Q[i].ind=i;
        Q[i].l--;
        Q[i].r--;
    }
    sort(Q,Q+q,cmp);
    int cl=0,cr=0;
    for (int i=0;i<q;i++)
    {
        int left=Q[i].l,right=Q[i].r;
        while(cl<left)
            remove(cl),cl++;
        while(cl>left)
            add(cl-1),cl--;
        while(cr<=right)
            add(cr),cr++;
        while(cr>(right+1))
            remove(cr-1),cr--;
        ans[Q[i].ind]=answer;
    }
    for (int i=0;i<q;i++)
        printf("%d\n",ans[i]);
    return 0;
}