leetcode_202題——Happy Number（雜湊）

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Happy Number Total Accepted: 7315 Total Submissions: 22724My SubmissionsQuestion Solution 

 

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

Credits:
Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

 

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     這道題將每次根據前一個值計算出來的結果儲存在set中，再進行尋找就可以了

#include<iostream>//#include<map>#include<set>using namespace std;int n_to_n(int a){int b=a;int last_result=0;while(b!=0){last_result=(b%10)*(b%10)+last_result;b=b/10;}return last_result;}bool isHappy(int n) {set<int> temp;temp.insert(n);int a=n;bool c;while(1){int b=n_to_n(a);if(b==1){c=1;break;}if(temp.count(b)==1){c=0;break;}temp.insert(b);cout<<b<<endl;a=b;}return c;}int main(){cout<<isHappy(2)<<endl;}

　　

leetcode_202題——Happy Number（雜湊）