Happy Number
浏览数：31 /
时间：2015年06月11日
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
- 1^2 + 9^2 = 82
- 8^2 + 2^2 = 68
- 6^2 + 8^2 = 100
- 1^2 + 0^2 + 02 = 1
思路： 我没啥思路。。直接上代码。但是在discussion里有些巧妙地解法。待洒家去看看。
1 public boolean isHappy(int n) { 2 HashSet<Integer> set = new HashSet<Integer>(); 3 while (!set.contains(n)) { 4 set.add(n); 5 int sum = 0; 6 while (n != 0) { 7 sum += (n % 10) * (n % 10); 8 n /= 10; 9 } 10 if (sum == 1) { 11 return true; 12 }else{ 13 n = sum; 14 } 15 } 16 return false; 17 }
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