Leetcode题目：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

题目解答：不断计算num各位数字的平方和，直到进入循环或最终结果为1，并返回对应的结果。

代码如下：

class Solution {
public:
    bool isHappy(int n) {
        if(n <= 0)
            return false;
        unordered_set<int> num_set;
        while((n != 1) && (num_set.find(n) == num_set.end() ) )
        {
            num_set.insert(n);
            n = getSum(n);
        }
        if(n == 1)
        {
            return true;
        }
        else
            return false;
       
    }
   
    int getSum(int n)
    {
        int sum = pow((n % 10),2) ;
        while(n / 10 != 0)
        {
            n = n / 10;
            int tmp = pow((n % 10),2);
            sum += tmp;
           
        }
        return sum;
    }
};

Leetcode题目：Happy Number

原文：http://www.cnblogs.com/CodingGirl121/p/5425031.html