leetcode 202

202. Happy Number

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

利用递归求解，出口设置为参数为1返回true，参数出现过则返回false.

代码如下：

 

class Solution {
public:
    int sum;
    vector<int> re;
    bool isHappy(int n) {
        if(n == 1)
        {
            re.clear();
            return true;
        }
        else
        {
            int count = 0;
            for(int i = 0; i < re.size(); i++)
            {
                if(n == re[i])
                {
                    count++;
                }
                if(count > 1)
                {
                    return false;
                }
            }
        }
        sum = 0;
        while(n)
        {
            sum += (n%10) * (n%10);
            n /= 10;
        }
        re.push_back(sum);
        return isHappy(sum);
    }
};