leetcode Happy Number

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題目串連

https://leetcode.com/problems/happy-number/  

Happy NumberDescription

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

$1^2 + 9^2 = 82$
$8^2 + 2^2 = 68$
$6^2 + 8^2 = 100$
$1^2 + 0^2 + 0^2 = 1$

class Solution {public:bool isHappy(int n) {if (1 == n) return true;set<int> A;while (true) {int v = 0;do {int i = n % 10;v += i * i;} while (n /= 10);if (1 == v) return true;if (A.find(v) != A.end()) return false;n = v;A.insert(n);}}};

leetcode Happy Number