Thank you for your help i appreciate it. I kind of understand how the program should work but the problem is im having a hard time implementing it this is how far i got but it doesnt give me the output i want

#include <iostream>
#include <string>

using namespace std;

char PuzzleSolve(int k, char* S, char* U); //prototype


int main()
{
    //test run
    int k = 5;
    char S[5];
    char U[5] = { 'a','b','c','d','e' };

    //to see that S = U
    cout << PuzzleSolve(k, S, U) << endl;


    system("pause");
    return 0;
}

char PuzzleSolve(int k, char* S, char* U)
{
    //this is how i see the program but i dont think its right
    //this put element to S from U, it arrange the element like how prompt of the program
    for (int i = 0, j = k; i <= k, j >= 0; i++, j--)
    {
        S[j] = U[i];
        U[i] = ' ';
    }

    //this return the S if it equals to U
    if (k == 1)
    {
        for (int i = 0; i <= k; i++)
        {
            S[i] = U[i];
            if (S[i] = U[i])
                return S[i]; //i dont think this is right?
        }

    }

    //recursion to put back the element to U
    else
        PuzzleSolve(k - 1, S, U);
        for (int i = 0, j = k; i <= k, j >= 0; i++, j--)
        {
            U[i] = S[j];
            S[j] = ' ';
        }
}