# HackerRank Lonely Integer problem solution

In this HackerRank Lonely Integer problem solution, we have Given an array of integers, where all elements but one occur twice, find the unique element.

## Problem solution in Python.

```def lonelyinteger(a):
a = sorted(a)
if len(a) < 3:
return a[0]
elif a[0] != a[1]:
return a[0]
else:
return lonelyinteger(a[2:])

if __name__ == '__main__':
a = int(input())
b = map(int, input().strip().split(" "))
print(lonelyinteger(b))```

## Problem solution in Java.

```import java.io.*;
import java.util.*;

class Bismillah {

public static void main(String[] args){
Scanner in = new Scanner(System.in);

int n = in.nextInt();
int[] ai = new int[n];
int i, j;
int x = 0;
boolean state;

for (i = 0; i < n; i++) {
ai[i] = in.nextInt();
}

for (i = 0; i < n; i++) {
state = true;
for (j = 0; j < i; j++) {
if (ai[i] == ai[j]) {
j = i;
state = false;
}
}
if (state == true) {
for (j = i+1; j < n; j++) {
if (ai[i] == ai[j]) {
j = n;
state = false;
}
}
if (state == true) {
x = i;
i = n;
}
}
}

System.out.println(ai[x]);
}
}```

## Problem solution in C++.

```#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <cstdlib>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
using namespace std;
int lonelyinteger(vector < int > a) {
int res = 0;
for(int i = 0;i<(int)a.size();i++)
res ^= a[i];
return res;
}
int main() {
int res;

int _a_size;
cin >> _a_size;
cin.ignore (std::numeric_limits<std::streamsize>::max(), '\n');
vector<int> _a;
int _a_item;
for(int _a_i=0; _a_i<_a_size; _a_i++) {
cin >> _a_item;
_a.push_back(_a_item);
}

res = lonelyinteger(_a);
cout << res;

return 0;
}```

## Problem solution in C.

```#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <assert.h>
int lonelyinteger(int a_size, int* a) {
int res = 0;
for(int i=0; i<a_size; i++){
res = res^a[i];
}
return res;

}
int main() {
int res;

int _a_size, _a_i;
scanf("%d", &_a_size);
int _a[_a_size];
for(_a_i = 0; _a_i < _a_size; _a_i++) {
int _a_item;
scanf("%d", &_a_item);

_a[_a_i] = _a_item;
}

res = lonelyinteger(_a_size, _a);
printf("%d", res);

return 0;
}```