Codeforces Round #592 (Div. 2), problem: (B) Rooms and Staircases

#include<bits/stdc++.h>
using namespace std;
#define sf scanf
#define pf printf
#define pb push_back
#define pii pair<int,int>
#define pob pop_back
#define all(a) a.begin(),a.end()
#define fio ios_base::sync_with_stdio(false); cin.tie(0);cout.tie(0);
#define i64 long long int
#define mem(x,y) memset(x,y,sizeof(x))
#define fill(arr,b) fill(arr, arr+sizeof(arr)/sizeof(arr[0]), b)

const double pi = acos(-1.0);
const int maxn = (i64)2e5+5;

int main()
{
    int t;
    cin >> t;

    while(t--)
    {
        int n,zero=0,one=0;
        cin >> n;
        string s;
        cin >> s;
        if(s[0]=='1' || s[n-1]=='1'){cout<<n*2<<endl;continue;}
        bool fg=true;
        int l,r;
        for(int i=0;i<n;i++)
        {
            if(s[i]=='1')
            {
                one++;
                if(fg){l=i;fg=false;}
                r=i;
            }
            else zero++;
        }
        if(one==0) cout<<n<<endl;
        else
        {
            int x=zero+(one*2);
            int y=(n-l)*2;
            int z=(r+1)*2;
            cout<<max(x,max(y,z))<<endl;
        }
    }

return 0;
}