Interview Bootcamp

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Solution: Counting Elements (easy)

Problem Statement

Given a list of integers, determine the count of numbers for which there exists another number in the list that is greater by exactly one unit.

In other words, for each number x in the list, if x + 1 also exists in the list, then x is considered for the count.

Examples:

  1. Example 1:

    • Input: [4, 3, 1, 5, 6]
    • Expected Output: 3
    • Justification: The numbers 4, 3, and 5 have 5, 4, and 6 respectively in the list, which are greater by exactly one unit.

  2. Example 2:

    • Input: [7, 8, 9, 10]
    • Expected Output: 3

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Ionut Enescu

Ionut Enescu

· 2 years ago

    public int countElements(int[] arr) {
        int count = 0;
        Set<Integer> mySet = new HashSet<>();

        for (int i = 0; i < arr.length; i++) {
            mySet.add(arr[i]);

            if (mySet.contains(arr[i] + 1) || mySet.contains(arr[i] - 1)) {
                count++;
            }
        }

        return count;
    }