leetcode之Happy Number
2015-06-08 21:35
411 查看
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
这道题很简单,思路大致如下,首先取这个数的每一位数,其次考虑到终止条件是1或者循环
最开始只判断了最终条件如果是1就结束的情况,忘记了如果无限循环会怎么样,于是没有AC。
从网上查找了一下资料,发现用HashSet 是比较合理的,首先add()方法会将不在集合中的元素加入,其次contain()方法会判断某个数是否在集合内,
因此写了两个函数,一个是得到下一个要判断的数,另一个是判断这个数是不是Happy Number
代码如下:
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
这道题很简单,思路大致如下,首先取这个数的每一位数,其次考虑到终止条件是1或者循环
最开始只判断了最终条件如果是1就结束的情况,忘记了如果无限循环会怎么样,于是没有AC。
从网上查找了一下资料,发现用HashSet 是比较合理的,首先add()方法会将不在集合中的元素加入,其次contain()方法会判断某个数是否在集合内,
因此写了两个函数,一个是得到下一个要判断的数,另一个是判断这个数是不是Happy Number
代码如下:
public class Solution { public boolean isHappy(int n) { HashSet<Integer> hash = new HashSet<Integer>(); while (n != 1) { if (hash.contains(n)) { return false; } hash.add(n); n = s(n); } return true; } public int s(int n){ int num = 0; while(n!=0){ int u = n/10; int v = n%10; n = u; num += v*v; } int result = num; return result; } }
相关文章推荐
- iOS的多屏适配 - AutoLayout
- android技术资料
- 苹果开发基础知识
- QQ聊天界面的布局和设计(IOS篇)-第二季
- Python Appium实现中文输入分享
- Android:Layout_weight的深刻理解
- [027] 微信公众帐号开发教程第3篇-开发模式启用及接口配置
- [026] 微信公众帐号开发教程第2篇-微信公众帐号的类型(普通和会议)
- [025] 微信公众帐号开发教程第1篇-引言
- Android-RadioButton&RadioGroup
- iOS自定义转场动画
- Android-ToggleButton&CheckTextView&CheckBox
- [024] 欢迎大家关注我的微信公众帐号小q机器人(xiaoqrobot)
- Android-Button
- Android屏幕适配全攻略(最权威的官方适配指导)
- SVN在Android Studio中的配置
- android的线性布局
- Android Service
- Android-TextView
- iOS开发—06音频处理(音乐播放器6)