YouTube link finder using C

Question

Question:
Input Format:
A string containing the URL to a YouTube video. The format of the string can be in "https://www.youtube.com/watch?v=kbxkq_w51PM" or the shortened "https://youtu.be/KMBBjzp5hdc" format.

Output Format:
A string containing the extracted YouTube video id.

Sample Input:
https://www.youtube.com/watch?v=RRW2aUSw5vU

Sample Output:
RRW2aUSw5vU

-------------------

My program:
#include <stdio.h>
#include <string.h>

int main() {
char a[100];
char f[100];

int l = 0, i, j = 0;
scanf("%s", a);
for(i = 0; a[i] != '\0'; i++) {
l++;
}

for(i = l; i > l - 12; i--) {
f[j++] = a[i];
}

for(i = 0; f[i] != '\0'; i++) {
printf("%c", f[i]);
}

return 0;
}

I'm getting output as 'No output', what's wrong here?

Answer 1

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

int main() {
char a[100];
char f[12];

int l = 0, i, j = 0;
scanf("%s", a);
for(i = 0; a[i] != '\0'; i++) {
l++;
}

for(i = l; i > l - 12; i--) {
f[j] = a[i];
j++;
}

for(i = 11; i > 0; i--) {
printf("%c", f[i]);
}

return 0;
}

#This changes worked for me :)

Answer 2

https://code.sololearn.com/cEa6Gb4EBxiW/?ref=app