How can I rank teams based off of head to head wins/losses
- by TMP
I'm trying to write an algorithm (specifically in Ruby) that will rank teams based on their record against each other. If a team A and team B have won the same amount of games against each other, then it goes down to point differentials.
Here's an example:
A beat B two times
B beats C one time
A beats D three times
C bests D two times
D beats C one time
B beats A one time
Which sort of reduces to
A[B] = 2
B[C] = 1
A[D] = 3
C[D] = 2
D[C] = 1
B[A] = 1
Which sort of reduces to
A[B] = 1
B[C] = 1
A[D] = 3
C[D] = 1
D[C] = -1
B[A] = -1
Which is about how far I've got
I think the results of this specific algorithm would be:
A, B, C, D
But I'm stuck on how to transition from my nested hash-like structure to the results.
My psuedo-code is as follows (I can post my ruby code too if someone wants):
For each game(g):
hash[g.winner][g.loser] += 1
That leaves hash as the first reduction above
hash2 = clone of hash
For each key(winner), value(losers hash) in hash:
For each key(loser), value(losses against winner):
hash2[loser][winner] -= losses
Which leaves hash2 as the second reduction
Feel free to as me question or edit this to be more clear, I'm not sure of how to put it in a very eloquent way. Thanks!
