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Add Permutations method to Cards

master
Trevor Slocum 3 years ago
parent
commit
b0126631ff
  1. 1
      CHANGELOG
  2. 26
      cards.go
  3. 12
      cards_test.go

1
CHANGELOG

@ -1,4 +1,5 @@
0.1.2:
- Add Permutations method to Cards
- Rename library from cards to joker
0.1.1:

26
cards.go

@ -141,6 +141,32 @@ func (c Cards) Reversed() Cards {
return cc
}
// Permutations returns all permutations of the supplied cards.
func (c Cards) Permutations() []Cards {
var permute func(Cards, int)
var res []Cards
permute = func(c Cards, n int) {
if n == 1 {
res = append(res, c.Copy())
} else {
for i := 0; i < n; i++ {
permute(c, n-1)
if n%2 == 1 {
tmp := c[i]
c[i] = c[n-1]
c[n-1] = tmp
} else {
tmp := c[0]
c[0] = c[n-1]
c[n-1] = tmp
}
}
}
}
permute(c, len(c))
return res
}
// Low returns the lowest valued card.
func (c Cards) Low() Card {
if len(c) == 0 {

12
cards_test.go

@ -73,6 +73,11 @@ func TestCards(t *testing.T) {
t.Errorf("failed to sort cards: expected %s, got %s", c.Sorted, sorted)
}
permutations := c.Cards.Permutations()
if len(permutations) != factorial(len(c.Cards)) {
t.Errorf("failed to generate permutations: expected %d, got %d: %s", factorial(len(c.Cards)), len(permutations), permutations)
}
low := c.Cards.Low()
if !low.Equal(c.Low) {
t.Errorf("failed to get low card: expected %s, got %s", c.Low, low)
@ -92,3 +97,10 @@ func BenchmarkCardsSort(b *testing.B) {
}
}
}
func factorial(i int) int {
if i <= 1 {
return 1
}
return i * factorial(i-1)
}

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