HackerRank•May 23, 2025

Arrays - DS

Hazrat Ali

HackerRank

An array is a data structure that stores elements of the same type in a contiguous block of memory. In an array, , of size , each memory location has some unique index,  (where ), that can be referenced as  or .

Your task is to reverse an array of integers.

Note: If you've already solved our C++ domain's Arrays Introduction challenge, you may want to skip this.

Example

Return .

Function Description

Complete the function  with the following parameter(s):

  • : the array to reverse

Returns

  • : the reversed array

Input Format

The first line contains an integer, , the number of integers in .
The second line contains  space-separated integers that make up .

Sample Input 1

 
4
1 4 3 2

Sample Output 1

 
2 3 4 1
 
 
Solution
#include <bits/stdc++.h>

using namespace std;

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

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


vector<int>& reverseArray(vector<int>& a) {
    int middle = a.size() / 2;
    for (int i = 0; i < middle; i++)
        swap(a[i], a[a.size() - i - 1]);

    return a;
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string arr_count_temp;
    getline(cin, arr_count_temp);

    int arr_count = stoi(ltrim(rtrim(arr_count_temp)));

    string arr_temp_temp;
    getline(cin, arr_temp_temp);

    vector<string> arr_temp = split(rtrim(arr_temp_temp));

    vector<int> arr(arr_count);

    for (int i = 0; i < arr_count; i++) {
        int arr_item = stoi(arr_temp[i]);

        arr[i] = arr_item;
    }

    vector<int> res = reverseArray(arr);

    for (size_t i = 0; i < res.size(); i++) {
        fout << res[i];

        if (i != res.size() - 1) {
            fout << " ";
        }
    }

    fout << "\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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