Golang combinations (not permutations) source https://www.sobyte.net/post/2022-01/go-slice/ https://go.dev/play/p/QX3svk0XJOV

combinations.go

package main

import (
	"fmt"
	"math/bits"
)

func main() {
	c := combinations([]string{"A", "B", "C"}, 2)
	fmt.Println(c)
}

func combinations(set []string, n int) (subsets [][]string) {
	length := uint(len(set))

	if n > len(set) {
		n = len(set)
	}

	// Go through all possible combinations of objects
	// from 1 (only first object in subset) to 2^length (all objects in subset)
	for subsetBits := 1; subsetBits < (1 << length); subsetBits++ {
		if n > 0 && bits.OnesCount(uint(subsetBits)) != n {
			continue
		}

		var subset []string

		for object := uint(0); object < length; object++ {
			// checks if object is contained in subset
			// by checking if bit 'object' is set in subsetBits
			if (subsetBits>>object)&1 == 1 {
				// add object to subset
				subset = append(subset, set[object])
			}
		}
		// add subset to subsets
		subsets = append(subsets, subset)
	}

	return subsets
}