fun swap(arr: CharArray, i: Int, j: Int) {
val tmp = arr[i]
arr[i] = arr[j]
arr[j] = tmp
}
fun printArray(arr: CharArray) {
println(arr.joinToString(" "))
}
// Recursive function to generate permutations
fun permute(arr: CharArray, l: Int, r: Int) {
if (l == r) {
printArray(arr)
return
}
for (i in l..r) {
swap(arr, l, i)
permute(arr, l + 1, r)
swap(arr, l, i) // backtrack
}
}
// Generate all combinations using bitmask
fun generateCombinations(arr: CharArray) {
val size = arr.size
for (mask in 1 until (1 shl size)) {
val combo = mutableListOf<Char>()
for (i in 0 until size) {
if ((mask and (1 shl i)) != 0) {
combo.add(arr[i])
}
}
println(combo.joinToString(" "))
}
}
fun main() {
val input = charArrayOf('a', 'b', 'c')
val size = input.size
println("All permutations:")
permute(input.copyOf(), 0, size - 1)
println("\nAll combinations:")
generateCombinations(input)
}
/*
run:
All permutations:
a b c
a c b
b a c
b c a
c b a
c a b
All combinations:
a
b
a b
c
a c
b c
a b c
*/
