LeetCode:Happy Number

標籤：

problem:

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

solution:  同迴圈小數的計算

class Solution {public:    bool isHappy(int n) {        unordered_set<int> markset;    //set儲存已出現的數字            if(n<1) return false;        if(n==1) return true;        markset.insert(n);        while(true)        {         int sum=0;         while(n)        {            sum+=(n%10)*(n%10);            n/=10;        }        if(sum==1)            return true;        else if(markset.find(sum)!=markset.end())            return false;        markset.insert(sum);        n=sum;         }    }};

 

LeetCode:Happy Number