LeetCode OJ：Happy Number（歡樂數）

標籤：

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

歡樂數，就是不斷將位的平方相加為新數，看看最後得到的數是不是1，是的話就是歡樂數，否則不是。代碼比較簡單，用一個set儲存下來已經求到過的不是1的數字，一旦

後期某個計算到的數字能在set中找到（不是1），那麼就一定進入到死迴圈當中了。這是就應該返回false， 否則一旦某個計算結果是1那麼久返回true，代碼見下：

 1 class Solution { 2 public: 3     bool isHappy(int n) { 4         set<int> sample; 5         sample.insert(n); 6         int s = 0; 7         for(;;){ 8             while(n != 0){ 9                 s += (n % 10) * (n % 10);10                 n /= 10;11             }12             if(s == 1)13                 return true;14             else{15                 if(sample.find(s) != sample.end())16                     return false;17                 sample.insert(s);18                 n = s;19                 s = 0;20             }21         }22     }23 };

 

LeetCode OJ：Happy Number（歡樂數）