import java.lang.Integer
/*
findNthSetBit32:
----------------
Given:
- x : a 32-bit integer
- n : which set bit to find (1-based index)
Returns:
A 32-bit mask with ONLY the Nth set bit of x turned on.
If n is larger than the number of set bits, returns 0.
Algorithm:
- Use Integer.numberOfTrailingZeros(x) to locate the lowest set bit.
- Remove that bit using x = x and (x - 1).
- When we reach the Nth one, return 1 shl index.
*/
fun findNthSetBit32(x0: Int, n0: Int): Int {
var x = x0
var n = n0
while (x != 0) {
// Index (0–31) of the lowest set bit
val index = Integer.numberOfTrailingZeros(x)
n -= 1
if (n == 0) {
return 1 shl index
}
// Remove the lowest set bit
x = x and (x - 1)
}
// Fewer than n set bits
return 0
}
/*
toBinary32:
-----------
Convert integer to a padded 32-bit binary string.
*/
fun toBinary32(x: Int): String {
val s = Integer.toBinaryString(x)
return s.padStart(32, '0')
}
fun main() {
val value = 0b00001101001101101100100010100000
val n = 4
val result = findNthSetBit32(value, n)
println("Input value: ${toBinary32(value)}")
println("N = $n")
println("Result mask: ${toBinary32(result)}")
}
/*
run:
Input value: 00001101001101101100100010100000
N = 4
Result mask: 00000000000000000100000000000000
*/
