Invert

#include <bits/stdc++.h>
#define ll long long
#define N (1<<17)

using namespace std;

ll v[2*N];
ll inv;

void val (ll k) {
  k += N;
  v[k]++;
  for (k /= 2; k >= 1; k /= 2) {
    v[k] = v[2 * k] + v[2 * k + 1];
  }
}

ll sum (ll a, ll b) {
  ll s = 0;
  a += N;
  b += N;
  while (a <= b) {
    if (a % 2 == 1) s += v[a++];
    if (b % 2 == 0) s += v[b--];
    a /= 2; b /= 2;
  }
  return s;
}

int main () {
  int n;
  cin>>n;
  for (int i = 0; i < n; i++) {
    int t;
    cin>>t;
    if (t == 1) {
      int x;
      cin>>x;
      val(x);
      inv += sum(x + 1 , 100002);
    } else if (t == 2) {
      int x;
      cin>>x;
      val(x);
      inv += sum(1, x - 1);
    } else if (t == 3) inv = 0;
    else cout<<inv<<endl;
  }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED