FIRST PROBLEM
1) Write a C++ program that accepts a string from the user and then replaces all occurrences of the letter 'e' with the letter 'x'.
for example
I input : exercise
the output will be : xxxrcix (replacing all 'e' with 'x')
we should use str.find ; str.length ; str.replace
SECOND PROBLEM
2) Write a C++ program that accepts both a string and a single character from the user. The program should determine how many times the character is contained in the string.