44 lines
1000 B
Go
44 lines
1000 B
Go
/*
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Package permutation implements Heap's algorithm for generating permutations of
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lists. It uses Go 1.18's new generics feature to provide a generic interface
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*/
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package permutation
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// GenSlice is a generic slice of data
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type GenSlice[T any] []T
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/*
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Permutations uses Heap's Algorithm to generate a list of all possible
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permutations of the provided list. Most slices will automatically coerce
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their type into a GenSlice[T] with no casting required
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*/
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func Permutations[T any](arr GenSlice[T]) []GenSlice[T] {
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var helper func(GenSlice[T], int)
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var res []GenSlice[T]
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helper = func(arr GenSlice[T], n int) {
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if n == 1 {
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var tmp GenSlice[T]
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for _, i := range arr {
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tmp = append(tmp, i)
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}
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res = append(res, tmp)
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} else {
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for i := 0; i < n; i++ {
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helper(arr, n-1)
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if n%2 == 1 {
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tmp := arr[i]
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arr[i] = arr[n-1]
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arr[n-1] = tmp
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} else {
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tmp := arr[0]
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arr[0] = arr[n-1]
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arr[n-1] = tmp
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}
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}
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}
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}
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helper(arr, len(arr))
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return res
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}
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