Write a function that allows to convert a string to the corresponding number (i.e. implement the atoi() C function)

Question

Sigiloso · Accepted Answer

int my_atoi(char* pStr) {
	
	if (pStr == NULL) {
		printf("ERROR: null string.
");		
		return -1;
	}

	int num = 0;

	int pos;
	for (pos = 0; ; pos++) {
		char currChar = *(pStr+pos);

		// Check whether the current char is not a digit
		if ( currChar  '9' )
			return num;

		// Read the number and add it to the 'num' variable
		num = (num*10) + (int) currChar - (int)'0';
	}
	return num;
}

Sigiloso · Answer

int atoi(char *s)
{
  int i = 0;
  while(*s)
  {
    i = (i<<3) + (i<<1) + (*s - '0');
    s++;
  }
  return i;
}

Sigiloso · Answer

int atoi(char *s)
{
  int i=0;
  while(*s)
  {
    i = i*10 + (*s- '0');
    s++;
  }
  return i;
}

Sigiloso · Answer

Try testing for the above to sample codes, I have not really tested it on any compilers.

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