leetcode202

public class Solution {
    private int SumSqares(int n)
        {
            //将一个数字的各个数位的值分开存储
            var list = new List<int>();
            do
            {
                var x = n % 10;
                list.Add(x);
                n = n / 10;
            } while (n != 0);

            var sum = 0;

            foreach (var l in list)
            {
                sum += l * l;
            }
            return sum;
        }

        public bool IsHappy(int n)
        {
            var list = new List<int>();//已经计算出来的值，用于判断是否出现循环

            while (n != 1 && !list.Contains(n))
            {
                list.Add(n);
                n = SumSqares(n);
            }

            if (n == 1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }
}

https://leetcode.com/problems/happy-number/#/description

补充一个python的实现：

class Solution:
    def isHappy(self, n: int) -> bool:
        s = set([n])
        while n != 1:
            sn = str(n)
            sums = 0
            for i in range(len(sn)):
                sums += int(sn[i]) ** 2
            if sums in s:
                return False
            s.add(sums)
            n = sums
        return True

使用集合s记录已经出现过的数字：

如果出现数字1，则返回True；

如果在出现重复的数字之前都没有出现过1，则返回False。