Language: C++

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <map>
 
using namespace std;
const int maxn=500000+5;
map<int,int> mp;
int data[maxn];
int a[maxn];
int ans[500000+5];
struct node{
    int l,r,id;
    bool operator<(node t)const{
        return r<t.r;
    }
}q[500000+5];
int sum(int i){
    int ans=0;
    while(i>0){
        ans+=data[i];
        i-=i&-i;
    }
    return ans;
}
void add(int i,int x){
    while(i<maxn){
        data[i]+=x;
        i+=i&-i;
    }
}
 
int main()
{
    int n, m;
    scanf("%d",&n); scanf("%d",&m);
	fill(data,data+n+2,0);
	mp.clear();
	for(int i=1;i<=n;i++){
		scanf("%d",&a[i]);
	}
	for(int i=0;i<m;i++){
		scanf("%d%d",&q[i].l,&q[i].r);
		q[i].id=i;
	}
	sort(q,q+m);
	int pre=1;
	for(int i=0;i<m;i++){
		for(int j=pre;j<=q[i].r;j++){
			if(mp[a[j]]!=0){
				add(mp[a[j]],-1);
			}
			add(j,1);
			mp[a[j]]=j;
		}
		pre=q[i].r+1;
		ans[q[i].id]=sum(q[i].r)-sum(q[i].l-1);
	}
	for(int i=0;i<m;i++){
		printf("%d\n",ans[i]);
	}
    return 0;
}

Compiler output:
a.cc: In function 'int sum(int)':
a.cc:23:14: error: reference to 'data' is ambiguous
   23 |         ans+=data[i];
      |              ^~~~
In file included from /usr/include/c++/14/string:53,
                 from /usr/include/c++/14/bits/locale_classes.h:40,
                 from /usr/include/c++/14/bits/ios_base.h:41,
                 from /usr/include/c++/14/ios:44,
                 from /usr/include/c++/14/ostream:40,
                 from /usr/include/c++/14/iostream:41,
                 from a.cc:1:
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:11:5: note:                 'int data [500005]'
   11 | int data[maxn];
      |     ^~~~
a.cc: In function 'void add(int, int)':
a.cc:30:9: error: reference to 'data' is ambiguous
   30 |         data[i]+=x;
      |         ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:11:5: note:                 'int data [500005]'
   11 | int data[maxn];
      |     ^~~~
a.cc: In function 'int main()':
a.cc:39:14: error: reference to 'data' is ambiguous
   39 |         fill(data,data+n+2,0);
      |              ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:11:5: note:                 'int data [500005]'
   11 | int data[maxn];
      |     ^~~~
a.cc:39:19: error: reference to 'data' is ambiguous
   39 |         fill(data,data+n+2,0);
      |                   ^~~~
/usr/include/c++/14/bits/range_access.h:344:5: note: candidates are: 'template<class _Tp> constexpr const _Tp* std::data(initializer_list<_Tp>)'
  344 |     data(initializer_list<_Tp> __il) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:334:5: note:                 'template<class _Tp, long unsigned int _Nm> constexpr _Tp* std::data(_Tp (&)[_Nm])'
  334 |     data(_Tp (&__array)[_Nm]) noexcept
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:323:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(const _Container&)'
  323 |     data(const _Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
/usr/include/c++/14/bits/range_access.h:312:5: note:                 'template<class _Container> constexpr decltype (__cont.data()) std::data(_Container&)'
  312 |     data(_Container& __cont) noexcept(noexcept(__cont.data()))
      |     ^~~~
a.cc:11:5: note:                 'int data [500005]'
   11 | int data[maxn];
      |     ^~~~