Question

The Collatz conjecture concerns what happens when we take any positive integer n and apply the following algorithm: if n is even 3 xn+1, if n is odd The conjecture states that when this algorithm is continually applied, all positive integers will eventually reach 1. For example, if n- 35, the sequence 1S 35, 106, 53, 160, 80, 40, 20, 10, 5, 16, 8, 4,2,'1 Write a C program using the fork) system call that generates this sequence in the child process. The starting number will be provided from the command line. For example, if 8 is passed as a parameter on the command line, the child process will output 8, 4, 2, 1. Because the parent and child processes have their own copies of the data, it will be necessary for the child to output the sequence. Have the parent invoke the wait) call to wait for the child process to complete before exiting the program. Perform necessary error checking to ensure that a positive integer is passed on the command line.

Answer 1

#include<stdio.h>
#include<stdlib.h>
#include<sys/wait.h>
#include<unistd.h>

int main(int argc, char **argv){
   int num;
  
   //checking - is there any argument passed or not
   if(argc==1){
        printf("\nNo extra command line argument passed other than program name.\n\n");
        exit(0);
    }
  

    // converting the char into integer
    num = atoi(argv[1]);
  
    //checking - is the argument positive interger or not
    if(num <= 0){
       printf("\nThe number should be a positive interger.\n\n");
        exit(0);
    }
  
    if(fork() == 0){
       //Child process
       while(num > 1){
           printf("%d ", num);
           if(num %2 == 0)
               num = num / 2;
           else
               num = 3 * num + 1;      
       }
       printf("1\n\n");
    }
    else{
       //Parent process - waiting for child to complete
       wait(NULL);
    }
  
    return 0;
}

OUTPUT:

rounak@rounak-HP-Notebook:/Desktop$ gcc a.c rounak@rounak-HP-Notebook:-/Desktop$ ./a.out -35 The number should be a positive interger rounak@rounak-HP-Notebook:-/Desktop$ ./a.out No extra command line argument passed other than program name. rounak@rounak-HP-Notebook:/Desktop$ ./a.out 35 35 106 53 160 80 40 20 10 5 16 8 4 2 1 rounak@rounak-HP-Notebook:-/Desktop$