Java中带指数的基本素因子分解

问题是： 任何正整数都可以表示为素数的唯一乘积，也称为其素因子分解。例如： 60=2^2*3*5

编写一个程序来计算正整数的素因子分解

输入：单个整数，n，其中n≥ 二,

输出：格式为“p^A*q^b*…”的字符串，其中p和q是素数，A和b是指数。如果指数为1，则应忽略它

我把其他的都记下来了，我只需要想办法把它写进“p^a*q^b*…”表格

这是我的密码：

import java.util.Scanner;

public class PrimeFactorization {
public static void main(String[] args) {

     // Input: A single integer, n, where n is greater than or equal to 2.

     System.out.println("Please input an integer greater than or equal to two!");
     System.out.println("This number will be factored.");
     Scanner inputNum = new Scanner(System.in);
     int toBFactored = inputNum.nextInt();

     // If the input does not fit the requirements, ask again for an input.

     while (toBFactored < 2) {
          System.out.println("Please input an integer greater than or equal to two.");
          toBFactored = inputNum.nextInt();
     }

     // Output: A string with the format: "p^a * q^b * ...", where p and q are
     // primes, and a and b are exponents. 
     // Decide first if a number (testNum) is prime.

     int primedecider = 0;
     for (int testNum = 2; testNum < toBFactored; testNum ++) {
          for (int factor = 2; factor < testNum; factor ++) {
               if (testNum % factor != 0 || testNum == 2) {
                    // Do nothing if prime.
               } else {
                    primedecider += 1;
                    // Add if composite.
               }
          }

          // If testNum is prime, if primedecider = 0, test if testNum divides
          // evenly into toBFactored.

          while (primedecider == 0 && toBFactored % testNum == 0 {
               System.out.print(testNum + " ");
               toBFactored /= testNum;
          }
     }
     System.out.print(toBFactored);

     inputNum.close();
}
}

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我对120的输出是2 3 5。如何将其转换为2^3*3*5？

如果不使用System.out.println打印因子， 如果你把它们放在一个列表中， 然后，这些函数将按照您描述的方式格式化它们。 当然，这只是众多方法中的一种

private String formatFactors(List<Integer> factors) {
    StringBuilder builder = new StringBuilder();

    int prev = factors.get(0);
    int power = 1;
    int factor = prev;

    for (int i = 1; i < factors.size(); ++i) {
        factor = factors.get(i);
        if (factor == prev) {
            ++power;
        } else {
            appendFactor(builder, prev, power);
            prev = factor;
            power = 1;
        }
    }
    appendFactor(builder, factor, power);

    return builder.substring(3);
}

private void appendFactor(StringBuilder builder, int factor, int power) {
    builder.append(" * ").append(factor);
    if (power > 1) {
        builder.append("^").append(power);
    }
}

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你的问题实际上与素因子分解无关；您的问题是计算列表中的重复元素：不要打印到System.out，而是将因子存储在数组中，然后签出此解决方案：。