LeetCode in Kotlin
47. Permutations II
Medium
Given a collection of numbers, nums, that might contain duplicates, return all possible unique permutations in any order.
Example 1:
Input: nums = [1,1,2]
Output: [[1,1,2], [1,2,1], [2,1,1]]
Example 2:
Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
Constraints:
1 <= nums.length <= 8-10 <= nums[i] <= 10
Solution
class Solution {
private var ans: MutableList<List<Int>>? = null
fun permuteUnique(nums: IntArray): List<List<Int>> {
ans = ArrayList()
permute(nums, 0)
return ans as ArrayList<List<Int>>
}
private fun permute(nums: IntArray, p: Int) {
if (p >= nums.size - 1) {
val t: MutableList<Int> = ArrayList(nums.size)
for (n in nums) {
t.add(n)
}
ans!!.add(t)
return
}
permute(nums, p + 1)
val used = BooleanArray(30)
for (i in p + 1 until nums.size) {
if (nums[i] != nums[p] && !used[10 + nums[i]]) {
used[10 + nums[i]] = true
swap(nums, p, i)
permute(nums, p + 1)
swap(nums, p, i)
}
}
}
private fun swap(nums: IntArray, i: Int, j: Int) {
val t = nums[i]
nums[i] = nums[j]
nums[j] = t
}
}