Leetcode 202 Happy Number

最新推荐文章于 2019-10-08 22:22:07 发布

转载最新推荐文章于 2019-10-08 22:22:07 发布 · 61 阅读

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原文链接：http://www.cnblogs.com/lilixu/p/4613178.html

本文介绍了一种用于判断正整数是否为快乐数的算法。快乐数是指通过将该数替换为其各位数字平方之和，重复该过程直到数字变为1或进入无限循环但不包括1的数字。文章给出了两种实现方案，一种使用JavaScript，另一种使用Python。

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: 19 is a happy number

12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

设定循环，如果最后无法得到1，必定存在某次情况使得得到的值等于之前生成过的值。

*js的Array没有内置contains/include函数，需要自己添加。

Array.prototype.contains = function (x) {
    for (var i in this)
        if (this[i] == x)
            return true
    return false
}

var isHappy = function(n) {
    var temp = []
    var s = n.toString()
    while (true){
        var sum = 0
        for (var i=0;i<s.length;i++)
            sum += s[i]*s[i]
        if(sum == 1) 
            return true
        else if (temp.contains(sum))
            return false
        temp.push(sum)
        s = sum.toString()
    }
}

class Solution(object):
    def isHappy(self, n):
        nums = []
        while True: 
            a = 0
            while n:
                a += (n%10)*(n%10)
                n /= 10
            if a == 1:
                return True
            if a in nums:
                return False
            else:
                nums.append(a)
                n = a