Multiple occurrences

You are given an integer array $A$. Your task is to calculate the sum of absolute difference of indices of first and last occurrence for every integer that is present in array $A$.

Formally, if element $x$ occurs $m$ times in the array at indices $B_1,B_2,B_3,...,B_m$, then the answer for $x$ will be $B_m-B_1$ if array $B$ is sorted.

You are required to calculate the sum of the answer for every such $x$ that occurs in the array.

Refer to sample notes and explanations for better understanding.

Example:

Input: N=5, arr[] = { 1, 2, 3, 3, 2 };
Output: 4

Approach

Java

import java.util.HashMap;

public class MultipleOccurrences {
    public static void main(String args[]) {
        int NN = 5;
        int arr[] = { 1, 2, 3, 3, 2 };
        HashMap<Long, Integer> indexes = new HashMap<Long, Integer>();
        long sum = 0;
        for (int i = 0; i < NN; i++) {
            long A_i = arr[i];
            if (indexes.containsKey(A_i)) {
                sum = sum + i - indexes.get(A_i);
            }
            indexes.put(A_i, i);
        }
        System.out.println(sum);
    }

}