如何在方法中编辑数组？

Question

所以这个方法叫做微分，它的目的是return一个由双精度数组组成的Poly对象，这个数组应该包含微分多项式的系数，例如如果提供一个poly对象包含带有 [2.0, 3.0, 2.0] 的数组，该方法将 return [4, 3, 0] 因为 2x^2 + 3x^1 + 2.0 的系数就是那些。

public static Poly polyObject;

public static String differentiate(Poly polyObject) {
    double[] array = polyObject.getDoubleArray();
    int counterVariable = array.length - 1;
    for (int i = 0; i < array.length; i++) {
        array[i] = array[i] * counterVariable;
        counterVariable--;
    }
}

不确定从这里要做什么才能更改数组的系数。

Answer 1

您可以 return 一个新的整数数组 int[] 例如：

public static int[] differentiate(Poly polyObject) {

    double[] array = polyObject.getDoubleArray();
    int counterVariable = array.length - 1;
    int[] coeffArray = new int[array.length];    

    for(int i = 0; i < array.length; i++) {
        coeffArray[i] = (int) array[i] * counterVariable;
        counterVariable--;
    }

    return coeffArray;
}

或更改同一个数组，但您将具有 double 类型值而不是 int。这正是您的代码，但不是 return 类型 String 而是将其更改为 void.

public static void differentiate(Poly polyObject) {

    double[] array = polyObject.getDoubleArray();
    int counterVariable = array.length - 1;

    for(int i=0; i < array.length; i++) {
        array[i] = array[i] * counterVariable;
        counterVariable--;
    }
}

Answer 2

应用Horner's method即可得到结果。这也显示了结果系数。

原方程=y = 2x^3 + 6x^2 +4x + 3
推导后=y' = 6x^2 + 12x + 4
给定x = 3，结果是54 + 36 + 4 = 94

使用Horner's Method解决让result = 0

result = result * x + 6 = 6 ( exp = 2)
result = result * x + 12 = 30 (exp = 1)
result = result * x + 4 = 94 (exp = 0) - done!

double[] coefs = { 2., 6., 4., 3 };
int exp = coefs.length-1;
double result = 0;
int i = 0;
int x = 3; // the value to be solve
while(i < exp) {
    coefs[i] *= (exp-i);
    result = result * x + coefs[i++];
}


// y = 2x^3 + 6x^2 +4x + 3
// After derivation. coefs = 6, 12, 4
// y' = 6x^2 + 12x + 4    =    54 + 36 + 4
coefs = Arrays.copyOf(coefs,coefs.length-1);
System.out.println(Arrays.toString(coefs));
System.out.println("result = " + result);

版画

[6.0, 12.0, 4.0]
result = 94.0

如何在方法中编辑数组？

How to edit the array within a method?

java

loops

polynomials