LeetCode【202】Happy Number

標籤：

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

題目也是比較簡單，AC代碼如下：

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，用到了尋找表，能省點時間就省點吧。

LeetCode【202】Happy Number