Created
October 1, 2024 18:37
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All permutations
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| package main | |
| import ( | |
| "fmt" | |
| ) | |
| func main() { | |
| r := permutation([]byte("abcdef")) | |
| for i := range r { | |
| pront(r[i]) | |
| } | |
| } | |
| func pront(s []byte) { | |
| for i := range s { | |
| fmt.Printf("%c", s[i]) | |
| } | |
| fmt.Printf("\n") | |
| } | |
| func factorial(i int) int { | |
| switch i { | |
| case | |
| 0, | |
| 1: | |
| return 1 | |
| case 2: | |
| return 2 | |
| } | |
| return i * factorial(i-1) | |
| } | |
| func swap[T any](s []T, i, j int) { | |
| s[i], s[j] = s[j], s[i] | |
| } | |
| /* | |
| 1 2 3 4 swap(0, 0) | |
| 1 2 3 4 swap(0, 1) | |
| 2 1 3 4 swap(0, 2) | |
| 3 1 2 4 swap(0, 3) | |
| 4 1 2 3 | |
| */ | |
| func permutation[T any](s []T) [][]T { | |
| l := len(s) | |
| switch l { | |
| case 0: | |
| return [][]T{} | |
| case 1: | |
| return [][]T{ | |
| {s[0]}, | |
| } | |
| case 2: | |
| return [][]T{ | |
| {s[0], s[1]}, | |
| {s[1], s[0]}, | |
| } | |
| } | |
| results := make([][]T, factorial(l)) | |
| c := 0 | |
| for i := range s { | |
| swap(s, 0, i) | |
| p := s[0] | |
| tails := permutation(s[1:]) | |
| for j := range tails { | |
| tails[j] = append([]T{p}, tails[j]...) | |
| results[c] = tails[j] | |
| c++ | |
| } | |
| swap(s, 0, i) | |
| } | |
| return results | |
| } |
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