LeetCodeOJ_202_Happy Number

答题链接

题目:

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

分析:

注意：整数2~9同样需要进行平方和操作，不能直接认定结果不等于1。

代码：

class Solution {public:    bool isHappy(int n) {          int cycle_num=0;          while(cycle_num<100){                vector<int> nums;              do{                  nums.push_back(n%10);//向vector里添加元素                  n=n/10;              }while(n!=0);              vector<int>::iterator it;              int sum=0;              for(it=nums.begin();it!=nums.end();it++)              {                 sum+=(*it)*(*it);              }              cycle_num++;              n=sum;            };          if(n==1)             return true;          else              return false;    }};

结果：