import Foundation
/*
removeBitsAndShift(number, positions)
-------------------------------------
Removes multiple bit positions from a number and shifts the remaining bits
right to fill the gaps.
Important:
Bits must be removed from highest → lowest position.
Otherwise earlier removals shift the positions of later ones.
*/
func removeBitsAndShift(number: Int, positions: [Int]) -> Int {
// Sort positions descending
let sorted: [Int] = positions.sorted(by: >)
var result: Int = number
for pos: Int in sorted {
let left: Int = result >> (pos + 1) // bits above removed bit
let right: Int = result & ((1 << pos) - 1) // bits below removed bit
result = (left << pos) | right // merge
}
return result
}
/*
printBinary(n)
--------------
Prints a 32-bit binary representation of an integer.
*/
func printBinary(_ n: Int) {
let binary: String = String(n, radix: 2).leftPadding(toLength: 32, withPad: "0")
let grouped: String = stride(from: 0, to: 32, by: 4)
.map { i in
let start = binary.index(binary.startIndex, offsetBy: i)
let end = binary.index(start, offsetBy: 4)
return String(binary[start..<end])
}
.joined(separator: " ")
print(grouped)
}
// Helper extension for padding
extension String {
func leftPadding(toLength: Int, withPad: String) -> String {
if self.count >= toLength { return self }
return String(repeating: withPad, count: toLength - self.count) + self
}
}
// Main program
let number: Int = 1234 // 0000 0000 0000 0000 0000 0100 1101 0010
let positions: [Int] = [1, 3, 7] // remove bits 1, 3, 7 (0 = LSB)
print("Original number in binary:")
printBinary(number)
let result: Int = removeBitsAndShift(number: number, positions: positions)
print("\nNumber after removing bits {1, 3, 7} and shifting remaining bits:")
printBinary(result)
print("\nResult as integer: \(result)")
/*
run:
Original number in binary:
0000 0000 0000 0000 0000 0100 1101 0010
Number after removing bits {1, 3, 7} and shifting remaining bits:
0000 0000 0000 0000 0000 0000 1001 0100
Result as integer: 148
*/
