HackerRank•May 12, 2025

Lonely Integer

Hazrat Ali

HackerRank

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

Example

The unique element is .

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, , the number of integers in the array.
The second line contains  space-separated integers that describe the values in .

Constraints

  • It is guaranteed that  is an odd number and that there is one unique element.
  • , where .

Sample Input 0

1
1

Sample Output 0

1

Explanation 0

There is only one element in the array, thus it is unique.

Sample Input 1

3
1 1 2

Sample Output 1

2

Explanation 1

We have two 's, and  is unique.

Sample Input 2

5
0 0 1 2 1

Sample Output 2

2

Solution
#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'lonelyinteger' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts INTEGER_ARRAY a as parameter.
 */


int lonelyinteger(vector<int>& a) {
    sort(a.begin(), a.end());
    int i = 0;
    while ((i <= a.size() - 1) && !(a[i] ^ a[i + 1])) {
        i += 2;
    }
    cout << a[i] << endl;
    return a[i];
}
int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string n_temp;
    getline(cin, n_temp);

    int n = stoi(ltrim(rtrim(n_temp)));

    string a_temp_temp;
    getline(cin, a_temp_temp);

    vector<string> a_temp = split(rtrim(a_temp_temp));

    vector<int> a(n);

    for (int i = 0; i < n; i++) {
        int a_item = stoi(a_temp[i]);

        a[i] = a_item;
    }

    int result = lonelyinteger(a);

    fout << result << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}





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