Step by Step solution about How to resolve the algorithm Repeat a string step by step in the C programming language

C Function string_repeat

The string_repeat function takes two arguments:

• n: The number of times to repeat the given string.
• s: The string to be repeated.

It returns a pointer to a new allocated string consisting of the given string repeated n times.

Implementation Details:

• It first calculates the length of the input string (slen).
• Then, it allocates memory for the new string, which will be n times the length of the input string plus one for the null-terminator.
• Using a for loop, it copies the input string to the allocated memory n times.
• Finally, it adds the null-terminator and returns the pointer to the new string.

C Function string_repeat (Alternative Implementation)

This is an alternative implementation of the string_repeat function that uses a different approach to achieve the same result:

• It first allocates memory for the new string, similar to the previous implementation.
• It then initializes two pointers, pa and pb, to point to different ends of the allocated memory.
• pa points to the first character of the new string, while pb points to the last character.
• It copies the input string to the end of the allocated memory, starting from the end.
• Then, it uses a while loop to copy the characters from the end of the input string to the beginning of the new string, overwriting any existing characters.
• Finally, it returns the pointer to the new string.

C Function char_repeat

The char_repeat function takes two arguments:

• n: The number of times to repeat the given character.
• c: The character to be repeated.

It returns a pointer to a new allocated string consisting of the given character repeated n times.

Implementation Details:

• It allocates memory for the new string, which will be n characters plus one for the null-terminator.
• It uses memset to fill the allocated memory with the given character.
• Finally, it adds the null-terminator and returns the pointer to the new string.

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

char * string_repeat( int n, const char * s ) {
  size_t slen = strlen(s);
  char * dest = malloc(n*slen+1);

  int i; char * p;
  for ( i=0, p = dest; i < n; ++i, p += slen ) {
    memcpy(p, s, slen);
  }
  *p = '\0';
  return dest;
}

int main() {
  char * result = string_repeat(5, "ha");
  puts(result);
  free(result);
  return 0;
}


...
char *string_repeat(const char *str, int n)
{
   char *pa, *pb;
   size_t slen = strlen(str);
   char *dest = malloc(n*slen+1);

   pa = dest + (n-1)*slen;
   strcpy(pa, str);
   pb = --pa + slen; 
   while (pa>=dest) *pa-- = *pb--;
   return dest;
}


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

char * char_repeat( int n, char c ) {
  char * dest = malloc(n+1);
  memset(dest, c, n);
  dest[n] = '\0';
  return dest;
}

int main() {
  char * result = char_repeat(5, '*');
  puts(result);
  free(result);
  return 0;
}