LeetCode:Happy Number

Happy Number

Total Accepted: 41299 Total Submissions: 121770 Difficulty: Easy

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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思路：

1.使用map(map<int,int> mapint)，将n置为1（mapint[n]=1）;

2.计算各数的平方和t，将t置1(mapint[t]=1);n=t;

3.当1==n时，true;

4.当map中出现重复数时，false

code:

class Solution {public:    bool isHappy(int n) {        map<int,int> mapint;        while(n!=1) {            if(mapint[n]) return false;            mapint[n]=1;            int t=0;            while(n) {                t += (n%10)*(n%10);                n /= 10;            }            n=t;        }        return true;    }};