leetcode-Happy Number

最新推荐文章于 2020-05-07 11:25:40 发布

原创最新推荐文章于 2020-05-07 11:25:40 发布 · 323 阅读

0 ·

CC 4.0 BY-SA版权

leetcode 专栏收录该内容

21 篇文章

订阅专栏

本文介绍了一种用于判断一个正整数是否为快乐数的算法。快乐数是指通过反复替换该数为它每个位数的平方和，最终得到1的数字。文章提供了C++实现代码，并解释了使用unordered_set进行循环检测的过程。

Question:

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

Solution:

class Solution {
    public:
    bool isHappy(int n) {
        if(n == 0){
            return false;
        }
        n = getNum(n);
        unordered_set<int> mset;
        while(mset.insert(n).second){
            if(n == 1){
                return true;
            }
            n = getNum(n);
        }
        return false;
    }
    int getNum(int n){
        int res = 0;
        while(n){
            int tmp = n % 10;
            res += tmp * tmp;
            n /= 10;
        }
        return res;
    }
};

总结：

unordered_set的函数insert返回值中各个版本都不一致：

(1)
pair