leetcode:Happy Number

最新推荐文章于 2018-07-17 09:21:10 发布

martin_liang

最新推荐文章于 2018-07-17 09:21:10 发布

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本文介绍了一种用于判断正整数是否为快乐数的算法。快乐数是指通过将该数替换为其各位数字平方之和并重复此过程，最终能得到1的正整数。文章详细展示了如何使用C++实现这一算法，并通过实例解释了整个判断流程。

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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

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