Inversions

#include <iostream>
#include <cmath>
#include <algorithm>
#include <bitset>
#include <vector>
 
using namespace std;
 
typedef long long ll;
 
 
 
 
int main() {
 
  string s;
  cin >> s;
 
  vector<bool> b;
  for (auto c : s) {
    b.push_back(c=='1');
  }
 
  int n = b.size();
  
  ll codd = 0;
  ll ceven = 0;
  for (int i=0; i<n; i++) {
    codd += b[i]^(i&1);
    ceven += !(b[i]^(i&1));
  }
  
  cout << min(codd, ceven) << endl;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED