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 + 0^2 = 1
LeetCode上的原题，请参见我之前的博客Happy Number。
解法一：
class Solution { public: /** * @param n an integer * @return true if this is a happy number or false */ bool isHappy(int n) { set<int> s; while (n != 1) { int t = 0; while (n) { t += (n % 10) * (n % 10); n /= 10; } n = t; if (s.count(n)) break; else s.insert(n); } return n == 1; } };
解法二：
class Solution { public: /** * @param n an integer * @return true if this is a happy number or false */ bool isHappy(int n) { while (n != 1 && n != 4) { int t = 0; while (n) { t += (n % 10) * (n % 10); n /= 10; } n = t; } return n == 1; } };
本文转自博客园Grandyang的博客，原文链接：快乐数[LintCode] Happy Number ，如需转载请自行联系原博主。
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