Lonely Integer - Given an array of integers, where all elements but one occur twice, find the unique element. Hackerrank Solution

Given an array of integers, where all elements but one occur twice, find the unique element.

Example

a = [1, 2, 3, 4, 3, 2 ,2]

The unique element is 4.

Function Description

Complete the lonelyinteger function in the editor below.

lonelyinteger has the following parameter(s):

·       int a[n]: an array of integers

Returns

·       int: the element that occurs only once

Input Format

The first line contains a single integer,n , the number of integers in the array.
The second line contains n space-separated integers that describe the values in a.

Constraints

·       1 <= n < 100

·       It is guaranteed that n is an odd number and that there is one unique element.

·       0 <= a[i] <= 100, where 0 <= i < n.

In Java 

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;


// solution
class Result {
  
  public static int lonelyinteger(List a) {
    int count = 0;
    ArrayList al = new ArrayList<>();
    for (Integer i : a) {
      count = 0;
      for (Integer j : a) {
        if (i==j) {
          count += 1;
        }
      } 
      if(count == 1){
        al.add(i);
      }
    }
    return al.get(0);
  }
}



public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        int n = Integer.parseInt(bufferedReader.readLine().trim());

        List a = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        int result = Result.lonelyinteger(a);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}

In Python

import math
import os
import random
import re
import sys

def lonelyinteger(a):
  for i in a:
    count = 0
    for j in a:
      if i == j:
        count += 1
    if count == 1:
      return i

if __name__ == '__main__':
    fptr = open(os.environ['OUTPUT_PATH'], 'w')

    n = int(input().strip())

    a = list(map(int, input().rstrip().split()))

    result = lonelyinteger(a)

    fptr.write(str(result) + '\n')

    fptr.close()