# [LintCode] Happy Number 快乐数

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## [LintCode] 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

1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

LeetCode上的原题，请参见我之前的博客Happy Number

```class Solution {
public:
/**
* @param n an integer
* @return true if this is a happy number or false
*/
bool isHappy(int n) {
set<int> s;
while (n != 1) {
int t = 0;
while (n) {
t += (n % 10) * (n % 10);
n /= 10;
}
n = t;
if (s.count(n)) break;
else s.insert(n);
}
return n == 1;
}
};```

```class Solution {
public:
/**
* @param n an integer
* @return true if this is a happy number or false
*/
bool isHappy(int n) {
while (n != 1 && n != 4) {
int t = 0;
while (n) {
t += (n % 10) * (n % 10);
n /= 10;
}
n = t;
}
return n == 1;
}
};```

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