First occurrence of a number in a sorted array

Given a sorted array of numbers where each number is repeated multiple times,  design an algorithm to find the first occurrence of a given number.
for e.g.
input array: {2,2,2,3,4,5,5,5,6,6,6,7,7,7,7,12,12,15,19}
number: 6
Here number 6 is found in position 8,9 and 10 (0-indexed). However, 8 is the first index.

Approach:- Using binary search locate the block of numbers containing the list of target number.
Once the list is found, apply binary search on the block again.

Solution

Count number of 1's in a Number

Count the number of 1's in a number's representation.
E.g. Number 23 is 0001 0111
So there are 4 One's

Approach
Left Shift a number (equivalent to dividing by 2). Then if divided number is a double of original number, ignore. Else increment count (the original number is odd).
23 >> 1   gives 11
11 >> 1   gives 5
5  >> 1    gives 2
2 >> 1     gives 1

Solution