p202

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LeetCode p202 Happy Number 题解

1.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

题意：

判断一个数是否为快乐数，即在按如上规律运算时，最后会得到1.如果不是快乐数，则会得到一个循环。

2.解题思路:

见代码。。先找出了那个循环中的某个数。。然后进行比对，在为1之前陷入循环的话则不是快乐数。

3.代码

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public class Solution {
    public boolean isHappy(int n) {
        while (n != 1 && n != 4) {
			int s = 0;
			while (n != 0) {
				s += (n % 10) * (n % 10);
				n = n / 10;
			}
			n = s;
			s = 0;
		}
		return 1 == n;
    }
}

4.一些总结：