Thread: Creating a function that swaps two strings from within an array of strings

Hey everyone, I'm new to programming and I'm having difficulty with swapping strings now. I've to come up with a program that repeatedly prompts the user to enter a word until he types GO, which terminates the loop and causes the program to print out all possible permutations of the words entered. The execution trace should look like this:

Enter a word: many
Enter a word: dogs
Enter a word: jump
Enter a word: GO
many dogs jump
many jump dogs
....

I used recursion to solve this, and the idea for the recursion I'm using is from this link:

Write a program to print all permutations of a given string - GeeksforGeeks

Here is my code:

Code:

#include <stdio.h>#include <string.h>


void permute ( char input[][20], int index, int end );


void swap ( char *x, char *y );


int main() 
{
    char input [100][20] = {""}, ch;
    int n = 0, index = 0, a = 0;


    printf("Enter a word: ");
    while ( ( ch = getchar () ) != '\n' )
    {
        input [0][a] = ch;
        a++;
    }


    while ( strcmp ( input [n] , "GO" ) != 0 )
    {
        a = 0;
        n++;
        printf("Enter a word: ");
        while ( ( ch = getchar () ) != '\n' )
        {
            input [n][a] = ch;
            a++;
        }


    }


    permute ( input, index, n - 1 );


    return 0; 
}


void permute ( char input[][20], int index, int end )
{
    if ( index == end )
    {
        printf("%s\n", input [index] );
        return;
    }


    else
    {
        for ( int i = index; i <= end; i++ )
        {
            swap ( input [i], input [i+1]);
            permute ( input, index + 1, end );
            swap ( input [i], input [i+1] );


        }
    }
}


void swap ( char *x, char *y )
{
    char temp [20] = {""};


    strcpy ( temp, x );
    strcpy ( x, y );
    strcpy ( y, temp );


}

Here is my execution trace:

Enter a word: manyEnter a word: words
Enter a word: jump
Enter a word: GO
many
GO
jump
GO
words
jump




------------------
(program exited with code: 0)


Press any key to continue . . .
Terminate batch job (Y/N)?

I don't know why it does not work, I've tried using gdb to debug using the backtrace function, but I get a No Stack message.

Can someone help me out here? I've been stuck for hours. Thanks!