Sum of Count of Unique Numbers in all Subarrays

import java.util.*;

public class UniqueElementSubarray {
    // This function returns the count of unique elements for subarray a[l...r]
    public static int uniqueElementSubarray(int[] a, int l, int r) {
        // To store frequency
        Map<Integer, Integer> mp = new HashMap<>();

        // To count unique elements
        int count = 0;

        for (int i = l; i <= r; i++) {
            mp.put(a[i], mp.getOrDefault(a[i], 0) + 1);
            if (mp.get(a[i]) == 1) {
                count++;
            }
        }

        return count;
    }

    // Returns the sum of the count of unique numbers in all subarrays
    public static int countUniqueElements(int[] a) {
        int n = a.length;

        // To store the final answer
        int res = 0;
        for (int i = 0; i < n; i++) {
            for (int j = i; j < n; j++) {
                // Count the number of unique elements from
                // index i to index j and add to the result.
                res += uniqueElementSubarray(a, i, j);
            }
        }

        return res;
    }

    public static void main(String[] args) {
        int[] a = {2, 1, 3, 2};
        int ans = countUniqueElements(a);
        System.out.println("Sum of Count of Unique Numbers in all Subarrays: " + ans);
    }
}
//Contributed by Aditi Tyagi

import java.util.HashMap;

public class UniqueNumbersInSubarrays {
    // Returns Sum of Count of Unique Numbers in all Subarrays
    public static int countUniqueElements(int[] a) {
        int n = a.length;

        // To store the final answer
        int res = 0;
        for (int i = 0; i < n; i++) {

            // To store frequency
            HashMap<Integer, Integer> map = new HashMap<>();

            // To store the number of unique elements
            int count = 0;

            // To store the sum of unique numbers of all subarrays starting at index i.
            int sum = 0;

            for (int j = i; j < n; j++) {
                int currentElement = a[j];

                if (!map.containsKey(currentElement)) {
                    map.put(currentElement, 1);
                    count++;
                }

                sum = sum + count;
            }

            // Add the sum of unique numbers of all subarrays starting at index i to the final answer
            res = res + sum;
        }

        return res;
    }

    public static void main(String[] args) {
        int[] a = {2, 1, 3, 2};
        int ans = countUniqueElements(a);

        // Function Call
        System.out.println("Sum of Count of Unique Numbers in all Subarrays: " + ans);
    }
}

import java.util.*;

public class UniqueNumbersSubarrays {

    // Returns Sum of Count of Unique Numbers in all Subarrays
    public static int countUniqueElements(ArrayList<Integer> a) {
        int n = a.size();

        int totalSubarrays = n * (n + 1) / 2;

        // To store final answer
        int res = 0;

        // To store indexes of each element
        HashMap<Integer, ArrayList<Integer>> mp = new HashMap<>();

        // Iterate the array to store the index
        for (int i = 0; i < n; i++) {
            if (!mp.containsKey(a.get(i))) {
                mp.put(a.get(i), new ArrayList<>());
            }
            mp.get(a.get(i)).add(i);
        }

        // Iterate over the map to find the contribution of each unique element
        for (Map.Entry<Integer, ArrayList<Integer>> entry : mp.entrySet()) {
            ArrayList<Integer> arr = entry.getValue();
            arr.add(n);

            // Stores the length of index array
            int len = arr.size();

            // To find contribution of element x in the final answer
            int contribution = 0;

            // To store previous index of element x
            int p = -1;
            for (int j = 0; j < len; j++) {
                int indexDifference = arr.get(j) - p - 1;
                contribution += (indexDifference * (indexDifference + 1)) / 2;
                p = arr.get(j);
            }

            // Add contribution of each unique element to final answer
            res += (totalSubarrays - contribution);
        }

        return res;
    }

    // Driver code
    public static void main(String[] args) {
        int n = 4;
        ArrayList<Integer> a = new ArrayList<>(Arrays.asList(2, 1, 3, 2));
        int ans = countUniqueElements(a);

        // Function Call
        System.out.println("Sum of Count of Unique Numbers in all Subarrays: " + ans);
    }
}