Question

How to round a number to the previous power of 2 in Swift

Answer 1

import Foundation

/// Rounds an integer down to the previous power of 2.
/// - Returns: The previous power of 2 less than or equal to `n`.
func roundToPreviousPowerOf2(_ n: Int) -> Int {
    guard n > 0 else { return 0 }
    
    return 1 << (Int.bitWidth - n.leadingZeroBitCount - 1)
}

let num = 21

print("Previous power of 2: \(roundToPreviousPowerOf2(num))")




/*
run:
 
Previous power of 2: 16

*/

 

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