[leetcode]Happy Number

最新推荐文章于 2019-02-27 16:56:04 发布

Cabinathor

最新推荐文章于 2019-02-27 16:56:04 发布

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本文介绍了一个用于判断整数是否为快乐数的算法。快乐数定义为通过将数字转换为其各位数字的平方和，重复此过程直到得到1或陷入循环。通过设置已出现数字的集合来避免无限循环。

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From : https://leetcode.com/problems/happy-number/

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

</pre><pre name="code" class="cpp">class Solution {
public:
    bool isHappy(int n) {
        set<int> occurs;
        int sum = 0, m;
        while(true) {
            sum = 0;
            while(n) {
                m = n%10;
                n /= 10;
                sum += m*m;
            }

            if(sum == 1) {
                return true;
            }
            if(occurs.find(sum) == occurs.end()) {
                occurs.insert(sum);
            } else {
                return false;
            }
            n=sum;
        }
    }
};

public class Solution {
    public boolean isHappy(int n) {
        if(n <= 0) {
            return false;
        }
        Set<Integer> occ = new HashSet<Integer>();
        while(!occ.contains(n) && n != 1) {
            occ.add(n);
            int sum = 0;
            while(n > 0) {
                int k = n%10;
                sum += k*k;
                n /= 10;
            }
            n = sum;
        }
        return n == 1;
    }
}