Find_Missing_Elements.java

/*

You are given an integer array nums consisting of unique integers.

Originally, nums contained every integer within a certain range. However, some integers might have gone missing from the array.

The smallest and largest integers of the original range are still present in nums.

Return a sorted list of all the missing integers in this range. If no integers are missing, return an empty list.

 

Example 1:

Input: nums = [1,4,2,5]

Output: [3]

Explanation:

The smallest integer is 1 and the largest is 5, so the full range should be [1,2,3,4,5]. Among these, only 3 is missing.

Example 2:

Input: nums = [7,8,6,9]

Output: []

Explanation:

The smallest integer is 6 and the largest is 9, so the full range is [6,7,8,9]. All integers are already present, so no integer is missing.

Example 3:

Input: nums = [5,1]

Output: [2,3,4]

Explanation:

The smallest integer is 1 and the largest is 5, so the full range should be [1,2,3,4,5]. The missing integers are 2, 3, and 4.

 

Constraints:

2 <= nums.length <= 100
1 <= nums[i] <= 100

*/
import java.util.*;
class Find_Missing_Elements {
    public List<Integer> findMissingElements(int[] nums) {
        Arrays.sort(nums);
        int n = nums.length ;
        ArrayList<Integer> ans = new ArrayList<>();
        HashMap <Integer,Integer> map = new HashMap<>();
        for(int i = 0 ; i<n; i++){
            map.put(nums[i], map.getOrDefault(nums[i],0)+1);
        }
        int max = nums[n-1];
        int min = nums[0];
        for(int i = min ; i<max ; i++){
            if(!map.containsKey(i)){
                ans.add(i) ;
            }
        }
        return ans;
    }
}