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.

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注意c++中没有乘方运算符。

不要把异或搞混了。

代码

class Solution {
public:
bool isHappy(int n) {
set<int> s1;
while(n!=1)
{
int temp=0;
while(n>=10)
{
temp+=((n%10)*(n%10));
n=n/10;
}
temp+=(n*n);
if(s1.find(temp)!=s1.end())
{
return false;
}
s1.insert(temp);
n=temp;
}
return true;
}
};