202. 快乐数 | Happy Number

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example:

Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

编写一个算法来判断一个数是不是“快乐数”。

一个“快乐数”定义为：对于一个正整数，每一次将该数替换为它每个位置上的数字的平方和，然后重复这个过程直到这个数变为 1，也可能是无限循环但始终变不到 1。如果可以变为 1，那么这个数就是快乐数。

示例:

输入: 19
输出: true
解释:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

20ms

 1 class Solution {
 2     func isHappy(_ n: Int) -> Bool {
 3         var m:Int = n
 4         var got:Set<Int> = Set<Int>()
 5         while(m != 1 && !got.contains(m))
 6         {
 7             got.insert(m)
 8             var sum:Float = 0
 9             while(m != 0)
10             {
11                 sum += powf(Float(m % 10),2)
12                 m /= 10
13             }
14             m = Int(sum)
15         }
16           return m == 1
17     }
18 }

 1 class Solution {
 2     func isHappy(_ n: Int) -> Bool {
 3       var nT = n
 4
 5         while (nT != 1 && nT != 4) {
 6             var t = 0
 7             while (nT>0) {
 8                 t += (nT % 10) * (nT % 10)
 9                 nT /= 10
10             }
11             nT = t
12         }
13         return nT == 1
14     }
15 }

 1 class Solution {
 2
 3     func nextSum(n: Int) -> Int {
 4         var sum = 0
 5         var nn = n
 6         while nn > 0 {
 7             sum += (nn % 10) * (nn % 10)
 8             nn /= 10
 9         }
10
11         return sum
12     }
13
14     func isHappy(_ n: Int) -> Bool {
15         var ans = nextSum(n: n)
16         while ans > 4 {
17             ans = nextSum(n: ans)
18         }
19         return ans == 1
20     }
21
22 }

16ms

 1 class Solution {
 2     func isHappy(_ n: Int) -> Bool {
 3         guard n > 0 else {
 4             return false
 5         }
 6
 7         var set = Set<Int>()
 8         var n = n
 9
10         while n != 1 {
11             if set.contains(n) {
12                 return false
13             }
14             set.insert(n)
15
16             var res = 0
17             while n != 0 {
18                 res += (n % 10) * (n % 10)
19                 n = n / 10
20             }
21             n = res
22         }
23
24         return true
25     }
26 }

原文地址：https://www.cnblogs.com/strengthen/p/9744963.html