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
利用递归求解，出口设置为参数为1返回true，参数出现过则返回false.
代码如下：
class Solution {
public:
int sum;
vector<int> re;
bool isHappy(int n) {
if(n == )
{
re.clear();
return true;
}
else
{
int count = ;
for(int i = ; i < re.size(); i++)
{
if(n == re[i])
{
count++;
}
if(count > )
{
return false;
}
}
}
sum = ;
while(n)
{
sum += (n%) * (n%);
n /= ;
}
re.push_back(sum);
return isHappy(sum);
}
};