乘法后如何在數組中添加每個索引

Question

我不能保留兩個數組的相乘索引並將其相加，它總是保留並相乘最后一個索引。

對於此示例，我具有值{1、2、3}和權重{0.1、0.2、0.7}，它應該執行以下操作：1 * 0.1 + 2 * 0.2 + 3 * 0.7，將得到2.6。

我這樣做1 * 0.1、2 * 0.2和3 * 0.7沒問題，但是它只保留最后一個索引，而給我2.1。

public static void main(String[] args) 
{
    double[] values = {1, 2, 3};
    double[] weights = {0.1, 0.2, 0.7};
    System.out.println(weightedSum(values, weights));
}

public static double weightedSum(double[] values, double[] weights)
{
    double multiply = 0;    
    double sum = 0; 
    for (int i = 0; i < values.length; i++){ 
        multiply = values[i]*weights[i];
    }
    return multiply;
}

Answer 1

您返回的是multiply ，而不是對sum做任何事情。 相反，對被乘數執行加法運算，然后將它們加到sum 。 喜歡，

public static double weightedSum(double[] values, double[] weights) {
    double sum = 0;
    for (int i = 0; i < values.length; i++) {
        sum += values[i] * weights[i];
    }
    return sum;
}

Answer 2

只要兩個數組的長度相同，最簡單的解決方案如下：

    //Multiply two arrays of size 3 and output sum
    int arr1[] = {1,2,3};
    double arr2[] = {0.1, 0.2, 0.7};
    final int LENGTH = 3;
    double result = 0;
    for(int i=0; i < LENGTH; i++) {
        result += arr1[i]*arr2[i];
    }
    NumberFormat formatter = new DecimalFormat("#0.00");     
    System.out.println("The result is " + formatter.format(result));

Answer 3

// functional style - The easiest solution as long as two arrays are of same length is following:

public static double weightedSum(double[] values, double[] weights) {
    return IntStream.rangeClosed(1, values.length)
                    .mapToDouble( i -> values[i] * weights[i])
                    .sum();
}