[leetcode] 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

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

[Solution]

不是happy number的话，结果会出现循环，用set记录所有结果，出现重复则为false

bool isHappy(int n)
{
set<int> table;

table.insert(n);
while (1)
{
int k = 0;
while (n)
{
k += (n % 10) * (n % 10);
n /= 10;
}
if (k == 1)
return true;
if (table.find(k) != table.end())
return false;
n = k;
table.insert(n);
}
}