I cant solve chaning characters - c

Question

Required use of the function that returns the length of the string.
Write a function that receives two character chains (n1, n2). The function of the function is to check if the string n2 is the subscription of the string n1. The function returns the index of the first occurrence of the string n2 in the string n1 (if n2 is the string n1) or -1 (if n2 is not the string n1). assumption: the inscription n2 is shorter than the inscription n1.
Example: inscription n1: "Computer" inscription n2: "er" Function returns: 6
i did it and it work
#include <stdio.h>
#define LIMIT 50
char * string_in(char *string, char *substring);
char * get(char *string, int n);
int main(void)
{
// test string_in()
char string[LIMIT];
char substring[LIMIT];
char *substr_loc;
printf("Enter a string: ");
get(string, LIMIT);
while (string[0] != '\0')
{
printf("Enter a substring to look for: ");
get(substring, LIMIT);
substr_loc = string_in(string, substring);
if (substr_loc == NULL)
printf("%s not in %s\n", substring, string);
else
printf("%s found in %s at index %lu\n",
substring, string, substr_loc - string);
printf("Enter a string (empty line to quit): ");
get(string, LIMIT);
}
puts("Bye");
return 0;
}
char * string_in(char *string, char *substring)
{
// checks if substring is in string
// returns pointer to first location of substring
// in string or NULL if substring not in string
int i;
while (*string != '\0')
{
i = 0;
// check for substring at current location
while (*(string + i) == *(substring + i))
{
i++;
// if next char in substring is null, then match
// is found. return current location
if (*(substring + i) == '\0')
return string;
}
string++;
}
// no match
return NULL;
}
char * get(char *string, int n)
{
// wrapper for fgets that replaces first newline with null
char *return_value = fgets(string, n, stdin);
while (*string != '\0')
{
if (*string == '\n')
{
*string = '\0';
break;
}
string++;
}
return return_value;
}
the next step is
Write a part of the program that will replace all occurrences of the n2 string in the string n1 with the string (the character '*'). Use the function from a task point. Please tell me how to write this function
Example: n1: "Spectacle" n2: "c" string n1 after change. "Spe*ta*le"
void function(char * get, char * string_in)
int i = 0;
for ( i = 0; get[i]=!'\0';i++){
if (get[i] == string_in[o]
get[i] = '*';}
dont work;<

Answer 1

it is a bit more complicated if you the string which replaces another string is longer. Here you have simple functions.
size_t strstrIndex(const char *heap, const char *needle) // returns SIZE_MAX if not found
{
char *result = strstr(heap,needle);
return result ? result - heap : SIZE_MAX;
}
char *replace(const char *heap, const char *needle, const char *rep)
{
size_t pos = 0, nocc = 0;
size_t len = strlen(heap), nlen = strlen(needle), rlen = strlen(rep);
char *string;
char *wstr = (char *)heap;
while((pos = strstrIndex(wstr, needle)) != SIZE_MAX)
{
nocc++;
wstr += pos + nlen;
}
string = calloc(1, len + ((rlen > nlen) ? (rlen - nlen) * nocc : 0) + 1);
if(string)
{
wstr = string;
while((pos = strstrIndex(heap, needle)) != SIZE_MAX)
{
strncpy(wstr, heap, pos);
heap += pos + nlen;
wstr += pos;
strcpy(wstr, rep);
wstr += rlen;
}
if(*heap)
{
strcpy(wstr, heap);
}
}
return string;
}
int main()
{
char *heap = "Spectaclec";
printf("%s\n", replace(heap, "c", "*"));
printf("%s\n", replace(heap, "c", "*****"));
printf("%s\n", replace("ccSpecctaccleccX", "cc", "*****"));
}

Answer 2

This task is easy if you use the functions that comes with the C library:
void ReplaceString(char *pTarget, const char *pPattern)
{
char *p;
size_t PatternLength = strlen(pPattern);
// for all occurances of the pattern..
while (p = strstr(pTarget, pPattern))
{
// The function strstr found an occurance of the pattern.
// So it must be sufficient space in the target starting at the pointer p..
// replace the characters in the target
memset(p, '*', PatternLength);
}
}
If you should avoid functions for some academic purposes, you can implement your own versions of strlen, strstr, and memset. Your example shows a function string_in that looks like such version of `strstr.