54 lines
1.7 KiB
Kotlin
54 lines
1.7 KiB
Kotlin
/**
|
|
* File: permutations_ii.kt
|
|
* Created Time: 2024-01-25
|
|
* Author: curtishd (1023632660@qq.com)
|
|
*/
|
|
|
|
package chapter_backtracking.permutations_ii
|
|
|
|
/* Backtracking algorithm: Permutation II */
|
|
fun backtrack(
|
|
state: MutableList<Int>,
|
|
choices: IntArray,
|
|
selected: BooleanArray,
|
|
res: MutableList<MutableList<Int>?>
|
|
) {
|
|
// When the state length equals the number of elements, record the solution
|
|
if (state.size == choices.size) {
|
|
res.add(state.toMutableList())
|
|
return
|
|
}
|
|
// Traverse all choices
|
|
val duplicated = HashSet<Int>()
|
|
for (i in choices.indices) {
|
|
val choice = choices[i]
|
|
// Pruning: do not allow repeated selection of elements and do not allow repeated selection of equal elements
|
|
if (!selected[i] && !duplicated.contains(choice)) {
|
|
// Attempt: make a choice, update the state
|
|
duplicated.add(choice) // Record selected element values
|
|
selected[i] = true
|
|
state.add(choice)
|
|
// Proceed to the next round of selection
|
|
backtrack(state, choices, selected, res)
|
|
// Retract: undo the choice, restore to the previous state
|
|
selected[i] = false
|
|
state.removeAt(state.size - 1)
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Permutation II */
|
|
fun permutationsII(nums: IntArray): MutableList<MutableList<Int>?> {
|
|
val res = mutableListOf<MutableList<Int>?>()
|
|
backtrack(mutableListOf(), nums, BooleanArray(nums.size), res)
|
|
return res
|
|
}
|
|
|
|
/* Driver Code */
|
|
fun main() {
|
|
val nums = intArrayOf(1, 2, 2)
|
|
val res = permutationsII(nums)
|
|
|
|
println("Input array nums = ${nums.contentToString()}")
|
|
println("All permutations res = $res")
|
|
} |