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【Leetcode】Happy Number

时间:2016-06-12 02:27:23      阅读:161      评论:0      收藏:0      [点我收藏+]

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题目链接:https://leetcode.com/problems/happy-number/

题目:

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

思路:

如果计算结果中出现4或它自身,则不是快乐数。

算法

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  1. public boolean isHappy(int n) {  
  2.         char c[] = String.valueOf(n).toCharArray();  
  3.         int sum = 0;  
  4.         for (char t : c) {  
  5.             int x = Integer.parseInt(String.valueOf(t));  
  6.             sum += x * x;  
  7.         }  
  8.         if (sum == 1) {  
  9.             return true;  
  10.         } else if (sum == 4 || sum == n)  
  11.             return false;  
  12.         else if (isHappy(sum))  
  13.             return true;  
  14.         return false;  
  15.     }  

【Leetcode】Happy Number

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原文地址:http://blog.csdn.net/yeqiuzs/article/details/51622697

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