# LeetCode202. Happy Number（模拟）

## LeetCode202. Happy Number（模拟）

• Easy
• Accepted：210,079
• Submissions：476,146

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:

Input: 19
Output: true
Explanation:
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

### 链接

https://leetcode.com/problems/happy-number/

### 代码

• Runtime: 8 ms, faster than 69.65% of C++ online submissions for Happy Number.
• Memory Usage: 8.5 MB, less than 100.00% of C++ online submissions for Happy Number.
class Solution {
public:
bool isHappy(int n) {
unordered_set <int> uset;
int num;
while (n != 1)
{
num = 0;
while (n) // 每位数字累加平方和
{
num += (n % 10) * (n % 10);
n /= 10;
}
n = num;
if (uset.count(n) > 0) // 出现过
break;
else
uset.insert(n);
}
return n == 1;
}
};

The end.
2019年2月14日 星期四