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package ARRAYS;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class SingleElement {

    /**
     *This Class Takes an array nums where each integer in nums appears thrice except one. Find out the number that has appeared only once
     * 
     * Examples:
     * Input : nums = [2, 2, 2, 3]
     * Output : 3
     * Explanation : The integers 3 has appeared only once.
     *
     * Input : nums = [1, 0, 3, 0, 1, 1, 3, 3, 10, 0]
     * Output : 10
     * Explanation : The integers 10 has appeared only once.
     */

    public static int searchSingleElement(int [] nums) {

        Map<Integer,Integer> element = new HashMap<>();
        int num = 0;

        for (int i = 0; i < nums.length; i++) {
            if (element.containsKey(nums[i])) {
                element.put(nums[i],element.get(nums[i]) + 1);
            } else {
                element.put(nums[i],1);
            }
        }

        for (Integer key : element.keySet()) {
            if (element.get(key) == 1) {
                num = key;
            }
        }
        return num;
    }

    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);
        System.out.print("ENTER ARRAY SIZE -> ");
        int size = s.nextInt();
        System.out.print("ENTER ARRAY ELEMENTS -> ");
        int[] arr = new int [size];

        for (int i = 0; i < size; i++) {
            arr[i] = s.nextInt();
        }
        System.out.print("NUMBER -> -> " + searchSingleElement(arr));
    }
}