# Leetcode Happy Number

Source: Internet
Author: User

1. Topics

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 and replace the number by the Sum of the squares of its digits, and repeat the process until the number equals 1 (where it would stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 is happy numbers.

Example: is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1
2. Solving Solutions

`Class Solution {public:    bool Ishappy (int n) {        if (n < 1) {            return false;        }        if (n = = 1) {            return true;        }                Unordered_set<int> shownums;        Shownums.insert (n);        while (true) {            int sum = 0;            while (n! = 0) {               int onedigital = n;               n = N/10;               sum = sum + onedigital * onedigital;            }            if (sum = = 1) {                return true;            } else{                if (shownums.find (sum) = = Shownums.end ()) {                    shownums.insert (sum);                } else{                    return false;                }            }            n = sum;}}    ;`

idea: Use the balance and divide by 10 to get each digit number, add to judge. A set is also used to store the numbers that have occurred, and if repeated, the description is not a happy number.

http://www.waitingfy.com/archives/1678

Leetcode Happy Number

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