题目：

题解：

func isHappy(n int) bool {cycle := map[int]bool{4: true, 6: true, 37: true, 58: true, 89: true, 145: true, 42: true, 20: true}for n != 1 && !cycle[n] {n = step(n)}return n == 1
}func step(n int) int {sum := 0for n > 0 {sum += (n%10) * (n%10)n = n/10}return sum
}