Introduction - If you have any usage issues, please Google them yourself
Enter in the main function of a string main_str, calling function will main_str the longest word out into sub_str (the called function parameters required for the main_str and sub_str), the output string sub_str in the main function. Assume that the input string main_str in one or more words separated by spaces. If more than one word of the same length, the output of the last one.