Question

In this programming assignment, you will write C code that performs recursion. For the purpose of this assignment, you will keep all functions in a single source file main.c. Your main job is to write a recursive function that generates and prints all possible password combinations using characters in an array.

• In your main() function you will first parse the command line arguments. You can assume that the arguments will always be provided in the correct format. Remember that the command line arguments are always strings. You will have to convert them to integers or individual characters for your use.
  • The program execution will be similar to ./a.out M c1 c2 c3 ... N
  • M represents the number of allowable characters in the password.
  • Based on the value for M, the next set of arguments will be the allowable characters. For example, if M = 3, then the next 3 arguments will be the characters allowed in the password. c1 = 'a', c2 = 'b', c3 = 'c'. The values of c1, c2, c3 does not have to be in alphabetical order. It can be any of the 26 characters.
  • Another example, if M = 2, then there will only be 2 arguments: c1 = 'x', and c2 = 'y'.
  • N represents the maximum length of the password.
  • Using the value of M create a dynamic array of characters. Copy the next set of arguments c1, c2, ... into the array.
• Create a function called printPasswords().
  • This function will take in three parameters - N, M, and the array of allowable characters.
  • This function will not return anything.
  • This function will print all allowable passwords of length 1 <= length <= N, each on a separate line.
  • You can write as many helper functions as needed.

Following is an example output 1, when the program execution is ./a.out 3 a b c 2

a
b
c
aa
ab
ac
ba
bb
bc
ca
cb
cc

Following is an example output 2, when the program execution is ./a.out 2 a b 3

a
b
aa
ab
ba
bb
aaa
aab
aba
abb
baa
bab
bba
bbb

in C please.

Answer 1

Code:-

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
//following function prints all the possible paawords
void printPasswords(int m, char** arr,int n, char* ans)
{
   //if max allowed length of string is 0, return
   if(n==0)
   {
       return;
   }
   //print all the possible strings by adding a single character to existing ans string
   int i;
   for(i=0;i<m;i++)
   {
       //temp stores the answer fater adding a character at the end of ans and prints it
       char* temp = (char*)malloc(sizeof(ans));
       strcpy(temp,ans);
       strcat(temp,arr[i]);
       printf("%s\n",temp);
   }
   //calling recursion on all possible strings that can be generated
   for(i=0;i<m;i++)
   {
       char* temp = (char*)malloc(sizeof(ans));
       strcpy(temp,ans);
       strcat(temp,arr[i]);
       printPasswords(m,arr,n-1,temp);
   }
}
//driver function
int main(int argc, char *argv[])
{
   //assigns value of m
   int m = atoi(argv[1]);
   //assigns value on n
   int n = atoi(argv[argc-1]);
   //string array to store the characters passed as arguments
   char** arr =(char **)malloc(m*sizeof(char*));
   //initialising the answer string
   char* ans =(char*)malloc((n+1)*sizeof(char));
   ans = "";
   //initializing arr array
   int i;
   for(i=0;i<m;i++)
   {
       arr[i] = argv[i+2];
   }
   //calling print printPasswords
   printPasswords(m,arr,n,ans);
   return 0;
}

Input 1:-

Output 1:-

Input 2:-

Output 2:-

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