Sum of ones

#include <algorithm>
#include <iostream>
#include <queue>
#include <vector>
#include <cmath>

using namespace std;



long long GetLeftMostSetBit(long long n)
{
    long long pos = 0;

    while (n > 0) {
        pos++;
        n >>= 1;
    }

    return pos;
}

long long TotalSetBitsFrom1ToN(long long n)
{
    long long leftMostSetBitInd = GetLeftMostSetBit(n);

    long long totalRep, mod;
    long long nearestPow;
    long long totalSetBitCount = 0;
    long long addRemaining = 0;

    long long curr
        = 0; 

    for (long long i = 1; i <= leftMostSetBitInd; ++i) {
        nearestPow = pow(2, i);
        if (nearestPow > n) {
            long long lastPow = pow(2, i - 1);
            mod = n % lastPow;
            totalSetBitCount += mod + 1;
        }
        else {
            if (i == 1 && n % 2 == 1) {
                totalRep = (n + 1) / nearestPow;
                mod = nearestPow % 2;
                addRemaining = 0;
            }
            else {
                totalRep = n / nearestPow;
                mod = n % nearestPow;

                if (mod >= (nearestPow / 2)) {
                    addRemaining
                        = mod - (nearestPow / 2) + 1;
                }
                else {
                    addRemaining = 0;
                }
            }

            curr = totalRep * (nearestPow / 2)
                   + addRemaining;
            totalSetBitCount += curr;
        }

    }

    return totalSetBitCount;
}


int main()
{
    long long x;
    cin >> x;
    cout << TotalSetBitsFrom1ToN(x) << endl;
    return 0;
}
 

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED