mirror of
https://github.com/Threnklyn/advent-of-code-go.git
synced 2026-06-07 20:53:30 +02:00
alexchao26
91 lines
2.2 KiB
Go
91 lines
2.2 KiB
Go
package permutations
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// CreatePermutations docz
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func CreatePermutations(start, end int) [][]int {
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orig := make([]int, end-start+1)
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for i := start; i <= end; i++ {
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orig[i-start] = i
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}
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results := make([][]int, 0)
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resPointer := &results
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perm(resPointer, orig, 0)
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// fmt.Println(len(results)) // 120 = 5!
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return results
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}
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func perm(resPointer *[][]int, slice []int, index int) {
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if index == len(slice) {
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*resPointer = append(*resPointer, slice)
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// fmt.Println("appending", resPointer)
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} else {
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temp := slice[index]
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for i := index; i < len(slice); i++ {
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newSlice := make([]int, len(slice))
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copy(newSlice, slice)
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// fmt.Println(newSlice, slice)
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newSlice[index] = newSlice[i]
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newSlice[i] = temp
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perm(resPointer, newSlice, index+1)
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}
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}
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}
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// CreatePermutations will return a 2D slice containing permutations from zero to the inputted int
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// func CreatePermutations(size int) [][]int {
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// result := make([][]int, 0)
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// helper := func(digits []int, builder []int) {
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// newDigits := make([]int, len(digits))
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// copy(newDigits, digits)
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// if len(digits) == 0 {
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// // use the reference point in memory
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// result = append(result, builder)
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// } else {
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// for index, digit := range newDigits {
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// fmt.Println("append", append(newDigits[:index], newDigits[index+1:]...))
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// fmt.Println("builder", append(builder, digit))
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// helper(append(newDigits[:index], newDigits[index+1:]...), append(builder, digit))
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// // fmt.Println("looping")
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// }
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// }
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// }
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// helper([]int{0, 1, 2, 3, 4}, make([]int, 0))
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// return result
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// }
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// func nextPerm(p []int) {
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// for i := len(p) - 1; i >= 0; i-- {
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// if i == 0 || p[i] < len(p)-i-1 {
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// p[i]++
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// return
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// }
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// p[i] = 0
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// }
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// }
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// func getPerm(orig, p []int) []int {
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// result := append([]int{}, orig...)
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// for i, v := range p {
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// result[i], result[i+v] = result[i+v], result[i]
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// }
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// return result
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// }
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// CreatePermutations docz
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// func CreatePermutations() [][]int {
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// orig := []int{5, 6, 7, 8, 9}
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// results := make([][]int, 0)
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// for p := make([]int, len(orig)); p[0] < len(p); nextPerm(p) {
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// // fmt.Println(getPerm(orig, p))
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// results = append(results, getPerm(orig, p))
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// }
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// return results
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// }
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