Questions

rand()  returns a random number

random()  returns a random number in a specified range

srand()  initialise a random number generator with a given seed value

randomize()   initializes a random number generator with a random value based o time.

Our solution:

Toss the coin twice.
Let TH, HT and TT correspond to the three choices.
And if you get HH, just repeat (so it takes 8/3 tosses on average).


BIASED COIN

If the coin was biased, TH and HT would occur with equal probability.
So you could assign THHT, HTTH and THTH to the three choices, with other 4-toss outcomes rejected.
Or you could assign HTT, THT and TTH to the three choices, with other 3-toss outcomes rejected.

Starting from letter 'S' add 5 in the clock wise direction to get the next letter in English alphabets.

Here S + 5 => 19 + 5 = 24 => X

X + 5 = 24 + 5 = 3 => C

Similarly, 

B + 5 = G