I’d love to see an algebraic Solution.
Since the numbers were reasonable, I “brute forced” the problem and luckily caught on to a pattern.
Rules:
win 2 in a row it is over
win 4 total it is over.
Start with the easiest scenario: 2 games
A - A
or
B - B
They could also play 3 games:
A - B - B
or
B - A - A
We can also have them play 4 games:
A - B - A - A
or
B - A - B - B
Since once we get 2 wins in a row the tournament ends, we can do 2 ways each for:
5 games
A - B - A - B - B
or
B - A - B - A - A
And 6 games
A - B - A - B - A - A
or
B - A - B - A - B - B
The tricky part is realizing there is 4 ways for the tournament to be played for 7 total games
Option 1: no team wins 2 in a row and the team who wins 1st ends up as the 4th win
A - B - A - B - A - B - A
or
B - A - B - A - B - A - B
Option 2: the team that wins 2nd, goes on to win the last 2 games for a total of 4
A - B - A - B -A - B - B
or
B - A - B - A - B - A - A
There are 14 ways the tournament can be played.
(B)
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