202. 快乐数 - 力扣（LeetCode）

主要是用到了鸽巢原理，最后他们一定会重合，我们只需要判断类似，链表的成环相遇的时候是不是1就行了

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