[Leetcode 202, Easy] Happy Number

最新推荐文章于 2020-04-30 11:11:07 发布

simplify2012

最新推荐文章于 2020-04-30 11:11:07 发布

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分类专栏： Leetcode_easy 文章标签： leetcode

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本文介绍了一种用于判断任意正整数是否为快乐数的算法。快乐数是指通过反复替换为各位数字平方和的过程最终能够得到1的数字。文章提供了一个具体的例子来说明这一过程，并给出了C++和Java等语言实现该算法的示例代码。

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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

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

Analysis:

Solutions:

C++:

    bool isHappy(int n) {
        if(n == 0)
            return false;
            
        if(n == 1)
            return true;
            
        int max_loops = 100;
        int num = n;
        for(int i = 0; i < max_loops; ++i) {
            vector<int> digits;
            while(num != 0) {
                int digit = num % 10;
                digits.push_back(digit);
                num /= 10;
            }

            for(int i = 0; i < digits.size(); ++i)
                num += digits[i] * digits[i];
            
            if(num == 1)
                return true;
        }
        
        return false;
    }

Java :

Python: