LEET code --Happy Number

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

笨方法  把算好的記錄下來 每次去記  但是這樣浪費時間

事實上  會循環的數字是固定得
https://leetcode.com/discuss/79442/hashset-time-check-whether-the-loop-with-mathematical-proof

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bool isHappy(int n) { int *done=malloc(sizeof(int)*128); int size=0,happy=n; while(happy!=1){ done[size++]=happy; for(int i=0;i<size-1;i++)if(done[i]==happy)return false; int temp=0; while(happy/10){ temp+= pow(happy%10,2); happy/=10; } temp+=pow(happy%10,2); happy=temp; } return true; }