checking the max consecutive one sequence in a bitmap array(number)

check_consecutive_ones.cpp

// https://www.hackerrank.com/challenges/30-binary-numbers/problem

using namespace std;

int main(){
    int n;
    cin >> n;
    
    int count = 0;
    int old = 0;
    // one stupid way is to calculate what is the highest bit rank that a 1 is at.
    // for example, a number 8 will give you log(8) = 3, and +1 (for the zero bit)
    // so in total you need to check the number 4 times.
  
//    int bit = int(floor(log2(n))) + 1;
//    int checker = 1;
//    for(int i = 0; i <= bit; ++i) {
//         if ((n & checker) > 0) {
//             count++;
//         } else {
//             old = max(old, count);
//             count = 0;
//         }
//         checker = checker << 1;
//   }
  
    // A second method is simply shift the number right and bit and with lowest 0000 0001
    // Program exits when there is no 1 bits in the number.
    while(n > 0) {
        if ((n & 1) > 0) {
            count++;
        } else {
            old = max(old, count);
            count = 0;
        }
        n = n >> 1;
    }
    // This is very important that you update the results
    // because the while operation may keep adding the count when the highest bit is 1
    // and exit from there without updating the old max consective value.
    int result = max(old, count);
    
    cout << result;
    return 0;
}