google kickstart Street Checkers

#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstring>
#include <chrono>
#include <complex>
#define endl "\n"
#define ll long long int
#define vi vector<int>
#define vll vector<ll>
#define vvi vector < vi >
#define pii pair<int,int>
#define pll pair<long long, long long>
#define mod 1000000007
#define inf 1000000000000000001;
#define all(c) c.begin(),c.end()
#define mp(x,y) make_pair(x,y)
#define mem(a,val) memset(a,val,sizeof(a))
#define eb emplace_back
#define f first
#define s second
using namespace std;


int main()
{
	int T;
	cin>>T;
	for(int t=1;t<=T;t++)
	{

        ll l,r;

        cin>>l>>r;

        vi odd(r-l+1,0),even(r-l+1,0);

        int iter = floor(sqrt(r));

        for(int i=1; i<=iter; i++){
            if(i%2==0){
                int shift = l%i;

                for(int j=(shift)?(l+i-shift):l; j<=r; j+=i){
                    if(i>floor(sqrt(j))) continue;
                    even[j-l]++;
                    if(i*i==j) continue;
                    if((j/i)%2==1) odd[j-l]++;
                    else even[j-l]++;
                }
            } else{
                int shift = l%i;

                for(int j=(shift)?(l+i-shift):l; j<=r; j+=i){
                    if(i>floor(sqrt(j))) continue;
                    odd[j-l]++;
                    if(i*i==j) continue;
                    if((j/i)%2==1) odd[j-l]++;
                    else even[j-l]++;
                }
            }
        }

        ll ans = 0;

        for(int i=0; i<r-l+1; i++){
            if(abs(odd[i]-even[i])<=2) ans++;
        }

        // for(auto i : odd) cout<<i<<" ";
        // cout<<"\n";
        //
        // for(auto i : even) cout<<i<<" ";
        // cout<<"\n";
		cout<<"Case #"<<t<<": "<<ans<<endl;
	}
	return 0;
}