Bit string

input/code.cpp: In function 'int main()':
input/code.cpp:20:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll i = 0; i < s.size(); i++)
                   ~~^~~~~~~~~~
input/code.cpp:37:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(ll i = 0; i < s.size(); i++)
                   ~~^~~~~~~~~~
input/code.cpp:39:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(ll j = i; j < s.size(); j++)
                       ~~^~~~~~~~~~

#include <bits/stdc++.h>
 
using namespace std;
 
#define ll long long
 
 
 
int main()
{
    string s;
 
    cin >> s;
 
    vector<ll> n_1;
 
    ll ans = 0;
 
 
    for(ll i = 0; i < s.size(); i++)
    {
        if(i == 0)
        {
            if(s[0] == '0')
                n_1.push_back(0);
            else
                n_1.push_back(1);
        }
 
        else if(s[i] == '1')
            n_1.push_back(n_1[i - 1] + 1);
 
        else
            n_1.push_back(n_1[i - 1]);
    }
 
    for(ll i = 0; i < s.size(); i++)
    {
        for(ll j = i; j < s.size(); j++)
        {
            if(i == 0)
            {
                if(n_1[j] % 2 == 0)
                    ans++;
            }
            else if((n_1[j] - n_1[i - 1]) % 2 == 0)
                ans++;
        }
    }
 
    cout << ans;
    return 0;
}

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: TIME LIMIT EXCEEDED

Test 16

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 17

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 18

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 19

Group: 3

Verdict: TIME LIMIT EXCEEDED

Test 20

Group: 3

Verdict: ACCEPTED

Test 21

Group: 3

Verdict: ACCEPTED