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path: root/go/secret-handshake/secret_handshake.go
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package secret

var sign = map[int]string{
	1 << 0: "wink",
	1 << 1: "double blink",
	1 << 2: "close your eyes",
	1 << 3: "jump",
}

const rev = 1 << 4

func reverse(s []string) []string {
	for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
		s[i], s[j] = s[j], s[i]
	}
	return s
}

func Handshake(n int) []string {
	if n <= 0 {
		return nil
	}
	var s []string
	for i := 1; i < rev; i <<= 1 {
		if n&i != 0 {
			s = append(s, sign[i])
		}
	}
	if n&rev != 0 {
		s = reverse(s)
	}
	return s
}