Write a program that accepts a string from the user and inserts a : as the delimiter after every fi ve characters before printing the delimited string. Write a program containing the function...

Write a program that accepts a string from the user and inserts a : as the delimiter after every

fi ve characters before printing the delimited string.

Write a program containing the function str_replace(s, s1, s2) that replaces the fi rst

occurrence of substring s1 with s2 in the string s. The function must return a pointer to s if the

replacement is successful, or NULL otherwise. (HINT: Use the strstr function.)