string strstr() function

Question

https://code.sololearn.com/c0A25a10a6a2
Question:
8.11
Write and test the strstr() function.
output from codeblocks:
Enter a sentence: Use your brain and heart

Enter the string that you want to find: brain
Last position of brain in " Use your brain and heart " is 10

Can someone explain the line 10 and 20 the conditions i.e *s2 == 0 and *(p2+1) == 0 ?

Answer 1

@Martin Thank you so much for explaining