[LeetCode] Happy Number

浏览数：24 / 时间：2015年06月11日

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.

解题思路：

模拟法即可。用一个set记录所有计算过的n，若出现重复（循环），返回false，若n为1，返回true;

class Solution {
public:
    bool isHappy(int n) {
        if(n<=0){
            return false;
        }
        set<int> checkedNumber;
        while(n!=1){
            checkedNumber.insert(n);
            int tempN=0;
            while(n!=0){
                int num=n%10;
                n=n/10;
                tempN+=num*num;
            }
            n=tempN;
            if(checkedNumber.find(n)!=checkedNumber.end()){
                return false;
            }
        }
        return true;
    }
};

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[LeetCode] Happy Number