How to store a substring given a delimiter in C - c

Question

Let's say I have a series of data that's in this form:
"SomethingIDontCareAbout : SomethingICareAbout"
where the part after the ":" can vary in length of course.
The goal here is only storing the "SomethingICareAbout" substring efficiently. I made this function but the problem is that I'm storing both substrings,so it seems like a waste of memory. Any help to reduce to the time/space complexity?
char** ExtractKey(char* S)
{
int n = strlen(S);
int count = 0, i = 0, j = 0;
for(i = 0; i < n; i++)
{
if(S[i] == ':')
break;
count++;
}
char** T = (char**)malloc(2 * sizeof(char*));
T[0] = (char*)malloc((count + 1) * sizeof(char));
T[1] = (char*)malloc((n - count) * sizeof(char));
for(i = 0; i < count; i++) // inefficient ? cus we won't need T[0] [j]
{
T[0][j] = S[i];
j++;
}
T[0][j+1] = '\0';
j = 0;
for(i = count + 1; i < n; i++)
{
T[1][j] = S[i];
j++;
}
T[1][j+1] = '\0';
return T;
}

Answer 1

There is no reason to invent a search for a character in a string, or a copy of a string.
If the input data will live long enough for you to use the "value" part, just return a pointer to the value:
char* ExtractKey(char* S)
{
return strchr(S, ':');
}
If it doesn't, or if you for some reason need a separate copy:
char* ExtractKey(char* S)
{
return strdup(strchr(S, ':'));
}

Answer 2

Honestly, this could be done efficiently if strtok() was used to split those strings. I have designed the following code that parses each string of a 2-D array with a common delimiter that is : here.
Now, let's take a look into the code (notice the comments):
#include <stdio.h>
#include <string.h>
#define MAX_LEN 128
int main(void) {
// The 2-D string
char str[][MAX_LEN] = {"SomethingElse : SomethingToCareAbout",
"Something2 : SomethingToCare2",
"Unnecessary : Necessary"};
int size = sizeof(str) / sizeof(str[0]);
// Applying Variable-Length Array (valid in C)
char store_cared_ones[size][MAX_LEN];
for (int i = 0; i < size; i++) {
// Declaring a temporary pointer variable to obtain the required
// substring from each string
char *sub_str = NULL;
sub_str = strtok(str[i], ": ");
sub_str = strtok(NULL, ": ");
// Copying the 'sub_str' into each array element of 'store_cared_ones'
strcpy(store_cared_ones[i], sub_str);
}
// Displaying each of 'store_cared_ones'
for (int i = 0; i < size; i++)
fprintf(stdout, "%s\n", store_cared_ones[i]);
return 0;
}
Finally, let's see what that code does:
rohanbari#genesis:~/stack$ ./a.out
SomethingToCareAbout
SomethingToCare2
Necessary