(LeetCode)Happy Number -- 寻找快乐数
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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
Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.
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解题分析:
题意就是寻找一个符合每一位的平方和相加最后等于 1 的数,被称为Happy Number.
方法一,循环判断,如果满足要求,则返回True,不满足,返回False, 判断循环的话,可以用Dict记录之前的,重复出现
视为循环,则返回False.
# -*- coding:utf-8 -*-__author__ = 'jiuzhang'class Solution(object): def isHappy(self, n): num_dict = {} while True: num_dict[n] = True sum = 0 while(n > 0): sum += (n % 10) * (n % 10) n /= 10 if sum == 1: return True elif sum in num_dict: return False else: n = sum
方法二 : 在方法一的基础上进行修改,先计算出100以下的Happy Number 。其余的在套用公式。
# -*- coding:utf-8 -*-__author__ = 'jiuzhang''''optimized code'''class Solution(object): def isHappy(self, n): happySet = set([1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97]) while n > 99: n = sum([int(x) * int(x) for x in list(str(n))]) return n in happySet
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