2021-10-24：快乐数。编写一个算法来判断一个数 n 是不是快乐数。「快乐数」定义为：对于一个正整数，每一次将该数替换为它

package main

import "fmt"

func main() {
    n := 5
    if true {
        ret := isHappy1(n)
        fmt.Println(ret)
    }
    if true {
        ret := isHappy2(n)
        fmt.Println(ret)
    }
}
func isHappy1(n int) bool {
    set := make(map[int]struct{})
    for n != 1 {
        sum := 0
        for n != 0 {
            r := n % 10
            sum += r * r
            n /= 10
        }
        n = sum
        if _, ok := set[n]; ok {
            break
        }
        set[n] = struct{}{}
    }
    return n == 1
}

//// 实验代码
//public static TreeSet<Integer> sum(int n) {
//TreeSet<Integer> set = new TreeSet<>();
//while (!set.contains(n)) {
//set.add(n);
//int sum = 0;
//while (n != 0) {
//sum += (n % 10) * (n % 10);
//n /= 10;
//}
//n = sum;
//}
//return set;
//}

func isHappy2(n int) bool {
    for n != 1 && n != 4 {
        sum := 0
        for n != 0 {
            sum += (n % 10) * (n % 10)
            n /= 10
        }
        n = sum
    }
    return n == 1
}