Pop Count
The pop count or hamming weight of a number is the number of set bits (1s) in its binary representation. For example, the pop count of 6 (0110 in binary) is 2, since it has two 1 bits.
Pop count is used in several algorithms:
 Estimating set cardinality
 Identifying sparse vs dense bitmaps
 Measuring distance between binary strings
 Finding variation between sets
It can be calculated efficiently using bit tricks.
Example in Java:


Example in C++:


Example in Python:


In summary, the pop count of a number counts the set bits in its binary representation. It has applications in set operations, bitmaps, and binary strings.
Pop Count, also known as “Hamming Weight,” refers to the number of set bits (bits that are 1) in the binary representation of a given integer. Counting the number of set bits is a common operation in computer science and can be used in various applications like cryptography, data compression, and error detection.
Java
In Java, you can use bitwise operations to calculate the pop count.


n & 1
: Checks the least significant bit. If it’s 1, it adds to the count.n >>>= 1
: Rightshifts the bits ofn
, effectively dividing it by 2.
C++
In C++, the code structure is similar to Java.


n & 1
: Checks the least significant bit.n >>= 1
: Rightshifts the bits.
Python
In Python, you can achieve the same using a while loop.


n & 1
: Checks the least significant bit.n >>= 1
: Rightshifts the bits.
Key Takeaways
 Pop Count calculates the number of set bits in an integer.
 Bitwise operations are a fast and efficient way to calculate the pop count.
 The logic remains consistent across different programming languages like Java, C++, and Python.