LeetCode【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

题目也是比较简单，AC代码如下：

bool isHappy(int n) {
        if(n<=0)
            return false;
        else if(n==1)
            return true;
        else
        {
            int squSum=n;
            int LUT[10];
            for(int i=0;i<10;i++)
                LUT[i] = i*i;
            vector<int> sum;
            while(squSum!=1)
            {
                sum.push_back(squSum);
                int tmp=squSum;
                squSum=0;
                while(tmp>=10)
                {
                    squSum=squSum+LUT[tmp%10];
                    tmp=tmp/10;
                }
                squSum=squSum+LUT[tmp];
                if(squSum == 1)
                    return true;
                vector<int>::iterator result = find( sum.begin( ), sum.end( ), squSum);
                if(result != sum.end())
                    break;
            }
            return false;
        }
    }

注意下，用到了查找表，能省点时间就省点吧。