Bit string

input/code.cpp: In function 'int main()':
input/code.cpp:26:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=s.length();i++)
              ~^~~~~~~~~~~~
input/code.cpp:32:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=1;i<=s.length();i++)
              ~^~~~~~~~~~~~

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
 
#define fi first
#define se second
#define mp make_pair
#define pb push_back
 
typedef long long ll;
typedef pair<ll,ll> ii;
typedef vector<int> vi;
typedef unsigned long long ull;
typedef long double ld; 
typedef tree<ii, null_type, less<ii>, rb_tree_tag, tree_order_statistics_node_update> pbds;

int a[555555];
int main()
{
	ios_base::sync_with_stdio(0); cin.tie(0);
	string s; cin>>s;
	a[0]=0;
	for(int i=1;i<=s.length();i++)
	{
		a[i]=a[i-1]+(s[i-1]=='1');
	}
	ll ans=0;
	ll t[2]={1,0};
	for(int i=1;i<=s.length();i++)
	{
		ans+=t[a[i]&1];
		t[a[i]&1]++;
	}
	cout<<ans<<'\n';
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 1

Verdict: ACCEPTED

Test 7

Group: 1

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 2

Verdict: ACCEPTED

Test 12

Group: 2

Verdict: ACCEPTED

Test 13

Group: 2

Verdict: ACCEPTED

Test 14

Group: 2

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED

Test 17

Group: 3

Verdict: ACCEPTED

Test 18

Group: 3

Verdict: ACCEPTED

Test 19

Group: 3

Verdict: ACCEPTED

Test 20

Group: 3

Verdict: ACCEPTED

Test 21

Group: 3

Verdict: ACCEPTED