Week 10: Monday
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Q1. (60)

Input three strings s, t and w from the user. Assume that the strings do not
contain blank or any whitespace character.

Write a function that finds all occurrence of substring t in s, and replaces
them by w. The function returns the number of such occurences or replacements.
Assume that t and w are of the same size.

For example,
if the string s is "abcdefghidefjkl",
t is "def"
and w is "xyz",
then after replacement,
s becomes "abcxyzghixyzjkl"
and the function returns 2.

The parameters of the function replace_substring contains only pointers to
characters (not arrays):
	int replace_substring(char *s, char *t, char *w)

Q2. (40)

Input a 3x3 matrix of numbers from the user.

Write a program that computes and prints the median of the medians of each row,
the median of the medians of each column and the median of the entire matrix.

Note that median of a set of numbers is the middle value of the given numbers
when they are arranged in ascending order.