LeetCode (24) Happy Number, leetcodehappy

LeetCode (24) Happy Number, leetcodehappy
Description

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

This question is relatively simple. The question requires a positive integer to constantly sum the squares of numbers on each digit. If the number finally converges to 1, the number is happy number, otherwise, the program may be in a loop starting from a certain number. We only need to calculate this question based on rules and use a hash table to store existing numbers.

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