package q202

type void struct{}

func next(n int) int {
	ret := 0
	for n > 0 {
		digit := n % 10
		n /= 10
		ret += digit * digit
	}
	return ret
}

func isHappy(n int) bool {
	seen := map[int]void{n: {}}
	for {
		n = next(n)
		if n == 1 {
			return true
		}
		if _, ok := seen[n]; ok {
			return false
		}
		seen[n] = void{}
	}
}

var _ = isHappy