Question

原文：所以对于我的编程类介绍，我们必须找到用户输入的一系列数字的素因子（即59-65）。这里有很多解决方案的问题在于它们使用我们尚未在课堂上讨论过的数据，如数组，继续等等。它是一个非常基本的类。至于要求，我们必须使用我们在第一个for循环中调用的primeFact方法/函数。她指示我们在方法中使用while和for循环来获得主要因素，但每当我认为我有某些东西时，它就不会出现。任何帮助都非常感谢，我的代码如下。我真的只需要用方法部分帮助找到因子的算法。

编辑：这是我上传的最终解决方案。它可以工作，并且会给出给定数字范围内所有数字的所有素因子。

import java.util.Scanner;

public class PrimeFact {

public static void main(String[] args) {
    int start, stop;

    //Get input
    Scanner input = new Scanner(System.in);
    System.out.println("Please enter then two values with the lower value first");
    start = input.nextInt();
    stop = input.nextInt(); 
    input.close();

    //Displays for the start of the loop
    System.out.println("Starting value (at least two digits): "+start);
    System.out.println("Ending value (at least two digits): "+stop);
    System.out.println("Prime factors for numbers between "+start+" and "+stop);

    //Loop for the prime factors
    for (int num = start; num <= stop; num++) {
        primeFact(num);
    }
}

// Method for Prime Factoring
public static void primeFact(int num) {
    int divisor = 2;
    System.out.print(num+" = ");
    while (num>1) {
        if ((num%divisor) == 0) {
            System.out.print(divisor+" x ");    
            num=num/divisor;            
        } else {
            divisor++;
        }
    }
    System.out.print("1");
    System.out.println();
    }
}

Answer 1

public static void primeFact(int num) {
   System.out.print(num+" = ");
    for(int i=2;i<num;i++)
    {
        if(num%i==0)
        {
            if(isPrime(i))
            {
                System.out.println("Prime Factor for "+num+" is:"+i);
            }
        }

     }
   if(num==2)
     System.out.println("Prime Factor for "+num+" is:"+num);
 }
static boolean isPrime(int num){
  for(int i=2;i<num;i++)
    {
        if(num%i==0)
        {
            return false;
        }
    }
    return true;
  }

//if u want use while replace the for loop like
   public static void primeFact(int num) {
   System.out.print(num+" = ");      

    int i=2;
    while(i<num)
    {
        if(num%i==0)
        {
            if(isPrime(i))
            {
                System.out.println("Prime Factor for "+num+" is:"+i);
            }
        }
        i=i+1;
     }
     if(num==2)
     System.out.println("Prime Factor for "+num+" is:"+num);
 }
static boolean isPrime(int num){
  int i=2;
   while(i<num)
    {
        if(num%i==0)
        {
            return false;
        }
     i=i+1;
    }
    return true;
  }

Answer 2

你的方法非常接近解决方案。但你的while循环无效。

记住它应该是这样的：

while(<boolean statement>){
    //code here
}

我将引用我们正在检查“primality”的变量作为“num”

以下是如何使用while循环检查因子：

//remember, num is given to us in the parameters of primeFact(int num).

boolean isPrime = true; //we are optimistic.

//we start at 2 because everything is divisible by one
int posFact = 2; //short for "possible factor"

while(posFact < num){ //this will start at 2, and go to 1 less than num
    if(num % posFact == 0){ // "%" gives us remainder
        isPrime = false; // we now know it's not prime
        System.out.println("The number " + posFact + " is a factor of " + num + ".");
    }
    posFact++; //increments posFact up by 1
}

if(isPrime){ //This will only be true if the number is prime
    System.out.println("The number " + num + " is prime!");
}

我们可以使用for循环执行完全相同的操作：

//remember, num is given to us in the parameters.

boolean isPrime = true; //we are optimistic.

for(int posFact = 2; posFact < num; posFact++){ //posFact's initialization and incrementation was moved here.
    if(num % posFact == 0){ // "%" gives us remainder
        isPrime = false; // we now know it's not prime
        System.out.println("The number " + posFact + " is a factor of " + num + ".");
    }
}

if(isPrime){ //This will only be true if the number is prime
    System.out.println("The number " + num + " is prime!");
}

Java中的Prime Factoring - 简介编程

2 个答案: