[LeetCode] 448. Find All Numbers Disappeared in an Array

 Problem : https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/

Because all numbers in the array is in the range [1, n].  If all numbers exist in the array, we can always swap the numbers to make nums[i] = i + 1.

So try to swap the number to its correct position. Then iterate the array to find the missing number which nums[i] != i + 1

class Solution {
    fun findDisappearedNumbers(nums: IntArray): List<int> {
        for (i in 0 until nums.size) {
            while (nums[i] != i+1) {
                if (nums[nums[i] - 1] == nums[i]) {
                    break
                }
                
                val tmp = nums[nums[i] - 1]
                nums[nums[i] - 1] = nums[i]
                nums[i] = tmp
            }
        }
        
        val result = mutableListOf<int>()
        
        for (i in 0 until nums.size) {
            if (nums[i] != i + 1) {
                result.add(i+1)
            }
        }
        
        return result
    }
}