Distinct Permutations

main.go

package main

import (
	"fmt"
)

func main() {
	permuts := distinctPermutations([]int{1, 2, 2, 3, 4}, 3)
	fmt.Println(permuts)
}

func distinctPermutations(elems []int, l int) [][]int {
	m := map[int]bool{}
	set := make([]int, 0, len(elems))
	for _, i := range elems {
		if _, ok := m[i]; !ok {
			m[i] = true
			set = append(set, i)
		}
	}

	acc := [][]int{{}}
	sl := len(set)

	// outer loop for the desired length of each combination
	for i := 0; i < l; i++ {
		newAcc := [][]int{}
		// iterate over each element of the accumulator
		for _, curr := range acc {
			cp := make([]int, len(curr))
			copy(cp, curr)

			// iterate over each element of the original set
			for j := 0; j < sl; j++ {
				nr := append(cp, set[j])
				newAcc = append(newAcc, nr)
			}
		}
		acc = newAcc
	}

	return acc
}