将一个整数分解为质数的乘积

阳光穿透心脏的1/2处 2021-09-23 08:58 289阅读 0赞

题目：将一个整数分解为质数的乘积

（质数就是除了1和它本身之外,再也没有整数能被它整除的数.比如：2..3.5.7.11.13.17.19.23.39.31…………………………  
素数就是质数.质数之外的数称为合数.合数比如：4.6.8.16.32.64.72……………………………………  
但是注意,1既不是素数也不是合数.）

方式1：

import java.util.ArrayList;
    import java.util.List;
    import java.util.*;
    public class test1 {
    
    		    public static void main(String[] args) {
    		    	Scanner scanner=new Scanner(System.in);
    		    	 int n=scanner.nextInt();
    		        serch(n);
    		    }
    		    public static void serch(int n){
    		        List<Integer> list = new ArrayList<Integer>();
    		        int i = 2;
    		        int j = 0;
    		        System.out.print(n+"=");
    		        while (n >= 2) {
    		            if (n % i == 0) {
    		                list.add(i);
    		                n /= i;
    		                i = 2;
    		            }else {
    		                i++;
    		            }
    		        }
    		        int t=list.size()-1;
    		        for (Integer l : list){
    		            System.out.print(l);
    		            if (j<t) {
    		            	 System.out.print("*");
    		            	 j++;
    					}
    		            
    		        }
    	
    		    }
    }

如输入120，结果如下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hxeTE3MTkyMzkzMzc_size_16_color_FFFFFF_t_70][]

方式2：

import java.util.*;
    public class test1 {
    
    		    public static void main(String[] args) {
    		    	Scanner scanner=new Scanner(System.in);
    		    	 int n=scanner.nextInt();
    		    	 primeCount(n);
    		    }
    		    public static void primeCount(int num) {
    				StringBuffer sb = new StringBuffer();
    				sb.append(num + "=");
    				int minNumber = 2;// 定义最小的质数
    				while (minNumber < num) {
    					if (num % minNumber == 0) {
    						num = num / minNumber;
    						sb.append(minNumber + "*");
    					} else {
    						minNumber++;
    					}
    				}
    				sb.append(minNumber);
    				System.out.print(sb.toString());
    			}
    	}

输入90，结果如下

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hxeTE3MTkyMzkzMzc_size_16_color_FFFFFF_t_70 1][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hxeTE3MTkyMzkzMzc_size_16_color_FFFFFF_t_70]: /images/20210923/413c5cd0857240a4aef2d9533633c52c.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2hxeTE3MTkyMzkzMzc_size_16_color_FFFFFF_t_70 1]: /images/20210923/73936b9d2cd043a1aa9cfa6ce1c7f78a.png