[LeetCode]202. Happy Number 快乐数

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

1版：
将各个位之和存在数组里，如果有重复就不是快乐数。

class Solution {
public:
bool isHappy(int n)
{
if (n == 0)
return 0;
if (n == 1)
return 1;
int temp[400];
int t = 0;

while (n  > 0)
{
int i = 0;
while (n > 0)
{
i = i + (n % 10)*(n % 10);
n /= 10;
}
for (int j = 0; j < t; j++)
{
if (temp[j] == i) return false;
}
temp[t] = i;
t++;
if (i == 1)	return true;
else n = i;
}
}
};

2版：
别人的Solution中看到。
如果是快乐数，后者肯定会追上前者，如果不是，进入重复的循环也会到一样。

class Solution {
public:
int next (int n)
{
int sum = 0;
while(n)
{
sum += (n % 10)*(n % 10);
n /= 10;
}
return sum ;
}

bool isHappy(int num)
{
int a = num;
int b = next(num);
while (a != b)
{
a = next(a);
b = next(next(b));
}
return a==1;
}
};