728. Self-Dividing-Numbers

最新推荐文章于 2025-05-22 19:34:52 发布

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本文深入探讨了自除数的概念及其实现算法，自除数是指一个数能被其每一位数字整除的数，且不含0。文章提供了两种实现方法，一种是逐位检查，另一种是利用字符串转换提高效率。

A self-dividing number is a number that is divisible by every digit it contains.

For example, 128 is a self-dividing number because 128 % 1 == 0, 128 % 2 == 0, and 128 % 8 == 0.

Also, a self-dividing number is not allowed to contain the digit zero.

Given a lower and upper number bound, output a list of every possible self dividing number, including the bounds if possible.

Example 1:

Input: 
left = 1, right = 22
Output: [1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 15, 22]

Note:

The boundaries of each input argument are 1 <= left <= right <= 10000.

本菜鸟代码：

class Solution {
    public List<Integer> selfDividingNumbers(int left, int right) {
        List<Integer> list = new ArrayList();
        for(int i = left;i<=right;i++){
            if(selfDividingcheck(i)) list.add(i);
        }
        return list;
    }
    
    public boolean selfDividingcheck(int n){
        List<Integer> a = new ArrayList();
        int m = n;
        while(n>0){
           a.add(n%10);
           n = n/10;
        }
    
        for(int i = 0;i < a.size();i++){
            if(a.get(i)==0||(m%a.get(i) > 0)){
                a.clear();
                return false;
            } 
        }
        a.clear();
        return true;
    }
}

官方解答：

class Solution {
    public List<Integer> selfDividingNumbers(int left, int right) {
        List<Integer> list = new ArrayList();
        for(int i = left;i<=right;i++){
            if(selfDividingcheck(i)) list.add(i);
        }
        return list;
    }
    
    public boolean selfDividingcheck(int n){
        for(char c:String.valueOf(n).toCharArray()){
            if(c=='0'||(n%(c-'0')>0)) return false;
        }
        return true;
    }
}

官方用到了一个新的功能：

查询jdk8官方文档：

表示返回一个数的string类型。

再通过tocharArray()转换为一个个字符。这样就节省了时间。

实际上，只有两种toCharArray()方法;

CharArrayWriter:

This class implements a character buffer that can be used as an Writer. The buffer automatically grows when data is written to the stream. The data can be retrieved using toCharArray() and toString().

String类的方法：