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
class Solution {
public boolean isHappy(int n) {
HashSet set = new HashSet();
int re;
while(set.add(n)){
int sum =0;
while(n>0){
re = n%10;
sum += re * re;
n /= 10;
}
if(sum ==1) return true;
n = sum;
}
return n==1;
}
}
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原文来源：《202. Happy Number》
