[Leetcode 201, Medium] Bitwise AND of Numbers Range

Problem:

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

For example, given the range [5, 7], you should return 4.

Analysis:

Solutions:

C++:

    int rangeBitwiseAnd(int m, int n) {
        if(m == n)
            return m;

        unsigned int m_temp = m;
        unsigned int num_digits = 0;
        while(m_temp != 0) {
            ++num_digits;
            m_temp /= 2;
        }

        unsigned int new_number = 1;
        for(int i = 0; i < num_digits; ++i)
            new_number *= 2;

        if(new_number <= n)
            return 0;

        unsigned int result = m;
        for(unsigned int index = m + 1; index <= n; ++index)
            result &= index;

        return int(result);
    }

Java :

Python: