Happy Number

Desicription

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:

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Input: 19
Output: true
Explanation:
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 02 = 1

Solution

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class Solution {
private:
int fun(int n) {
int sum = 0;
while(n) {
sum += (n%10) * (n%10);
n /= 10;
}
return sum;
}
public:
bool isHappy(int n) {
int slow = n;
int fast = n;
do {
slow = fun(slow);
fast = fun(fast);
fast = fun(fast);
} while(fast != slow);
if(slow == 1)
return true;
else
return false;
}
};