Count bits in an integer

Problem:
Count the no. of 1's in an integer.

Solution:

Solution #1: The most straightforward approach is to check each bit one by one. Here is the code,

int count1(int n)
{
    int count=0;

    while(n)
    {
        if(n&1)
            count++;

        n = n>>1;
    }

    return count;
}

Solution #2: The below code is an efficient version which improves the average time.
This code is faster because on each iteration it always clears the LSB of the number.

int count2(int n)
{
    int count=0;

    while(n)
    {
        count++;
        n = n&(n-1);
    }

    return count;
}

Complexity:

time - O(1)
space - O(1)

Links and credits:
http://puddleofriddles.blogspot.ru/2012/03/count-bits-in-integer.html