202. Happy Number

最新推荐文章于 2024-01-10 13:13:11 发布

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最新推荐文章于 2024-01-10 13:13:11 发布

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分类专栏： LeetCode

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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，重复此过程直到数字变为1或进入无限循环但不包括1的数字。文章提供了一个具体的例子，即19被证明为快乐数的过程。

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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) {

        unordered_map<int, bool> numsMap;
        int res = 0;
        while ((res = getHappyNumber(n)) != 1) {       
            if (numsMap[res])
                return false;
            numsMap[res] = true;
            n = res;            
        }

        return true;
    }

private:
    int getHappyNumber(int num) {
        if (num == 0)
            return 0;

        int mod = num % 10;
        num /= 10;

        return mod * mod + getHappyNumber(num);
    }
};