leetcode202

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

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

還是比較簡單的題目，，雖然我提的次數比較多，，又拉低了通過率，真是無情。每次計算如果得到結果為1就返回true，否則，並把每個不是1的結果放在vector容器中，然後在下次的遍歷中，對產生的新值進行判斷，如果在容器中，就說明，發生了死迴圈，返回false，否則把值繼續加入到vector容器中即可。還是非常簡單的。

class Solution {
public:
    string atoi(int n)
    {
        string s;
        while (n)
        {
            int temp = n % 10;
            char c = temp + '0';
            s = c + s;
            n /= 10;
        }
        
        return s;
    }
    
    bool isHappy(int n) {
        vector<int> vi;
        vi.push_back(n);
        
        while (1)
        {
            string s = atoi(n);
            n = 0;
            for (int i = 0; i != s.size(); ++i)
            {
                n += (s[i] - '0') * (s[i] - '0');
            }
            if (n == 1)
            return true;
            else if (find(vi.begin(), vi.end(), n) != vi.end())
            return false;
            else
            vi.push_back(n);
        }
    }
};