Number of 1 Bits

1. Problem Description

Given an integer, output the number of 1s in its 32-bit binary representation. Negative numbers are represented using two’s complement.

2. Approach

• Bit shifting

3. Implementation

// Time: O(1)
// Space: O(1)
func NumberOf1(n int) int {
	count := 0
	bit := 1
	for i := 0; i < 32; i++ {
		if n&bit > 0 {
			count++
		}
		bit = bit << 1
	}
	return count
}

4. References

• Number of 1 Bits - NowCoder
• LCR 133. Number of 1 Bits - LeetCode
• Number of 1 Bits - LeetCode