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$ curl repovive.com/roadmaps/math-fundamentals/bit-manipulation/count-bits-implementation

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$ curl repovive.com/roadmaps/math-fundamentals/bit-manipulation/count-bits-implementation

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Count Bits - Implementation - Bit Manipulation | Math Fundamentals | Repovive

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Math Fundamentals18 sections · 842 units13h total

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Count Bits - Implementation

The code

Here's the complete solution using Brian Kernighan's algorithm:


function countBits(n)
    count := 0
    while n > 0
        n := n & (n - 1)    // Clear rightmost set bit
        count := count + 1
    return count

Each iteration clears one set bit. The loop runs exactly as many times as there are 1s in $n$ . Time complexity: $O(k)$ where $k$ is the number of set bits. Space complexity: $O(1)$ .