Non recursive Heap (1963) algorithm

heapPermutation.go

package main

import "fmt"

func generate(n int, a []int64) {
	var c = make([]int, n)
	fmt.Println(a)
	i := 0
	for i < n {
		if c[i] < i {
			if i%2 == 0 {
				a[0], a[i] = a[i], a[0]
			} else {
				a[c[i]], a[i] = a[i], a[c[i]]
			}
			fmt.Println(a)
			c[i]++
			i = 0
		} else {
			c[i] = 0
			i++
		}

	}
}

func main() {

	var digits = []int64{1, 2, 3, 4, 5, 6, 7, 8, 9}
	generate(len(digits), digits)

}