algorithm - Generate all permutations in go -

i looking way generate possible permutations of list of elements. similar python's itertools.permutations(arr)

permutations ([]) []  permutations ([1]) [1]  permutations ([1,2]) [1, 2] [2, 1]  permutations ([1,2,3]) [1, 2, 3] [1, 3, 2] [2, 1, 3] [2, 3, 1] [3, 1, 2] [3, 2, 1] 

with difference not care whether permutations generated on demand (like generator in python) or together. not care whether lexicographically sorted. need somehow these n! permutations.

there lot of algorithms generate permutations. 1 of easiest found heap's algorithm:

it generates each permutation previous 1 choosing pair of elements interchange.

the idea , pseudocode prints permutations 1 after outlined in above link. here implementation of algorithm returns permutations

func permutations(arr []int)[][]int{     var helper func([]int, int)     res := [][]int{}      helper = func(arr []int, n int){         if n == 1{             tmp := make([]int, len(arr))             copy(tmp, arr)             res = append(res, tmp)         } else {             := 0; < n; i++{                 helper(arr, n - 1)                 if n % 2 == 1{                     tmp := arr[i]                     arr[i] = arr[n - 1]                     arr[n - 1] = tmp                 } else {                     tmp := arr[0]                     arr[0] = arr[n - 1]                     arr[n - 1] = tmp                 }             }         }     }     helper(arr, len(arr))     return res } 

and here example of how use (go playground):

arr := []int{1, 2, 3} fmt.println(permutations(arr)) [[1 2 3] [2 1 3] [3 2 1] [2 3 1] [3 1 2] [1 3 2]] 

one thing notice permutations not sorted lexicographically (as have seen in itertools.permutations). if reason need sorted, 1 way have found generate them factorial number system (it described in permutation section , allows find n-th lexicographical permutation).

p.s. can take @ others people code here , here