JAVA 中的主要因素

Question

我正在尝试编写一个程序，将输出作为给定数字的质数分解。但是，我的代码作为 "2**2**2**2**2**5**7**7**11*" 的输出给出了正确的答案，但我希望它的特定输出为 "(p1**n1)(p2**n2)...(pk**nk)"。这是我的代码：

public class PrimeDecomp
{
    public static String factors(int n)
    {
        String ans = "";
        for (int i = 2; i <= n; i++)
        {
            if (n % i == 0)
            {
                // checks if i is a divisor of num
                ans += i + "**";
                // writes i in prime factorization
                n = n/i;
                // since it is written down, num=num/i
                i--;
                // just in case their are multiple factors of same number.
                // For example, 12=2*2*3
            }
        }
        return (ans.substring(0, ans.length() - 1));
    }

    public static void main(String[] args)
    {
        System.out.println(PrimeDecomp.factors(86240));
    }
}

Answer 1

您几乎明白了，与其一次计算一个因素，不如计算同一个因素的所有因素并计算它们：

public static String factors(int n)
{
    String ans = "";
    int count = 0;
    for (int i = 2; i <= n; i++)
    {
        // Reset the counter
        count = 0;

        /*
         * Instead of only processing on factor, we process them all and
         * count them
         */
        while (n % i == 0)
        {
            count++;
            n = n / i;
        }

        // If we have at least processed one add it to the string
        if (count == 1)
        {
            ans += "(" + i + ")";
        } else if (count > 0)
        {
            ans += "(" + i + "**" + count + ")";
        }
    }
    return ans;
}

由于您经常在循环中操作字符串，因此您应该使用 StringBuilder

JAVA 中的主要因素

Prime Factors in JAVA

java

output

decomposition