Question 1: String Replace Without Using Built-in Functions

Implement a function that will take three Strings as arguments and return the first string
with all instances of the second string replaced by the third string.

Do not use any of the standard regexp functions or string replace functions.

Example:
replace("AFoxRunsInTheField", "Fox", "Cat") => "ACatRunsInTheField"

Restriction: don't use string.replace or regex replace
Question 2: LinkedIn Connection Distance

LinkedIn is designed to connect people together, so that in people search and other related
areas LinkedIn will show a connection distance between two users.

E.g., Bob connects with Alice, and Alice connects with Frank, assuming there is no other
connections, then Bob and Frank's connection distance is 2.