You are given a 5-letter word (for example, abcde). Write a C-Program which outputs all possible unique 5 letter permutations of this word in a text file. There should be no repetition of letters in permutation (i. e. in our example, bacde is a valid permutation but bbcde is invalid. Use of library functions for generation of permutations is NOT allowed. The text file containing the output should be named as q3out. txt. Each word of the output must be on a separate line in the text file. The 5-letter input word should be read by your program from the console. Provide comments in your code. Submit your C code, and the q3out. txt file for the following inputs:
(a) parba
(b) arbca

See attachment 1 for code

See attachment 2 for the output of permuting letters of parba

See attachment 3 for the output of permuting letters of arbca

Explanation:

The program was implemented in C

The program uses a recursive function letterpermutation and a swap function to successfully implement the requirement of this question.

The letterpermutation function is defined here

void letterpermutation(char *mystring, int index1, int index2) {  

This lets the program writes to a file

  FILE *fptr;

This opens the file in an appending mode

  fptr = fopen("q3out.txt","a");

int i;

This checks for unique strings.

if (index1 == index2) {

If found, this appends the string to the text file

   fprintf(fptr,"%s\n",mystring); }

If otherwise

else{  

This iterates through the string

for (i = index1; i <= index2; i++)  {

The swap function is called to swap the characters of the string

 swap((mystring+index1), (mystring+i));  

This calls the function, recursively

letterpermutation(mystring, index1+1, index2);  

This further swaps the characters of the string

swap((mystring+index1), (mystring+i));  

} } }  

The swap function begins here and what it literally does is that it swaps characters of the input string to create a new string

void swap(char *ch1, char *ch2) {  

char temp;  

temp = *ch1;  *ch1 = *ch2;  *ch2 = temp; }

The main function begins here

int main() {  

This declares and initializes the string

char mystring[] = "ABCd"; // The string here can be changed

This calls the function to permute the string

letterpermutation(mystring, 0, strlen(mystring)-1);  

return 0; }

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