leetcode 202. Happy Number

202. Happy Number

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

用map来存出现过的数

class Solution {public:    bool isHappy(int n)     {        map<int,int> p;        while (n != 1 && p.find(n) == p.end())          {            int sum = 0;            p[n] ++;              while (n != 0)            {                sum += pow(n % 10, 2);                 n /= 10;            }            n = sum;        }        return n==1;       }};