Bit string

#include <bits/stdc++.h>

using namespace std;
typedef long long ll;
#define pii pair<int,int>
#define pll pair<ll,ll>
#define fr first
#define sc second
#define pb push_back
#define mp make_pair
#define forr(i,a,b) for(ll i=a;i<b;i++)
#define mod 100000007
#define eps 0.0000001
string x;
ll dp[500000][2],ans=0,n;
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);cout.tie(0);
cin>>x;n=x.length();
if(x[0]=='0')dp[0][0]=1,dp[0][1]=0;
else dp[0][0]=0,dp[0][1]=1;
forr(i,1,n)
{if(x[i]=='0')
{dp[i][0]=dp[i-1][0]+1;
 dp[i][1]=dp[i-1][1];}
else
{dp[i][0]=dp[i-1][1];
dp[i][1]=dp[i-1][0]+1;}}
forr(i,0,n)ans+=dp[i][0];
cout<<ans<<endl;
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: 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