LeetCode 202. Happy Number ( C++版)

最新推荐文章于 2021-06-29 17:45:10 发布

原创最新推荐文章于 2021-06-29 17:45:10 发布 · 1.1k 阅读

0 ·

CC 4.0 BY-SA版权

leetcode&剑指offer 专栏收录该内容

38 篇文章

订阅专栏

本文介绍了一种用于判断正整数是否为快乐数的算法。快乐数是指通过不断将其各位数字的平方相加的过程最终能够得到1的正整数。文章详细展示了如何实现这一算法，并通过一个具体的例子解释了其工作原理。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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:
    unsigned long SUM(int n)
    {
        int sum = 0;
        while(n){
            int c = n % 10;
            n = n / 10;
            sum += c*c;
        }
        return sum;
    }
    bool isHappy(int n) {
        set<int> allsum;
        //求平方和
        unsigned long sum = SUM(n);
        //若和在set里，且不等于1，return false；
        //若和不在set里，加入set,继续求和的平方和
        while(sum != 1){
            if(allsum.find(sum) == allsum.end()){//不在set中，则加入set
                allsum.insert(sum);
                sum = SUM(sum);
            }
            else
                return false;
        }
        return true;
    }
};