C++: #ifndef CS19_C_STRINGS_H_ #define CS19_C_STRINGS_H_ namespace cs19 {

 /** * Finds the first occurrence of the substring needle in the C-string haystack. The terminating null * chars ('\0') are not compared. * * @param haystack the string in which to search * @param needle the string for which to search * @return a pointer to the beginning of the located substring, or nullptr if the substring is not * found. */ const char *strstr(const char *haystack, const char *needle) { // TODO }