Question

说实话，我很难找到算法或理解这个问题。我在网上搜索过，但我找到的答案都没有帮助。问题说：编写一个方法来计算名为SpecialSeries的类中的序列之和。该方法的签名是：

public static double sumOfSeries(double x, int numTerms)

This is the Question

Answer 1

我认为这段代码足以计算你的系列：

<?php

include('db.php');

if(isset($_POST['update']))
{

   $hostname = "localhost";
   $username = "root";
   $password = "";
   $databaseName = "winc sports";

   $connect = mysqli_connect($hostname, $username, $password, $databaseName);



   $id = $_POST['id'];
   $fname = $_POST['fname'];
   $lname = $_POST['lname'];
   $age = $_POST['age'];
   $country=$_POST['country'];
    $phone=$_POST['phone'];
    $email=$_POST['email'];

    $select = "SELECT * FROM studens WHERE id = '$id'"; 
    $selected = mysqli_query($connect, $select); 
    $row = mysqli_fetch_assoc($selected); 
    if (empty($_POST['fname'])) {$fname = $row['fname'];} else {$fname = $_POST['fname'];}
    if (empty($_POST['country'])) 
    {
    $country = $row['country'];
    } 
    else {
    $country = $_POST['country'];
    }
    if (empty($_POST['id'])) {
    $id = $row['id'];
        } 
    else {
    $id = $_POST['id'];
    }
    if (empty($_POST['age'])) {$age = $row['age'];} else {$age = $_POST['age'];}
    if (empty($_POST['phone'])) {$phone = $row['phone'];} else {$phone = $_POST['phone'];}
    if (empty($_POST['email'])) {$email = $row['email'];} else {$email = $_POST['email'];}
   $query = "UPDATE students SET Fname= '$fname', Lname = '$lname', Nationality = '$country', PhoneNumber = '$phone', Email= '$email', Age = '$age' WHERE Id = '$id'";

   $result = mysqli_query($connect, $query);
   var_dump($result);
   if($result)
   {
       echo 'Data Updated';
   }else
   {
       echo 'Data Not Updated';
   }
   mysqli_close($connect);
}

?>

<!DOCTYPE html>

<html>

    <head>

        <title>PHP INSERT DATA USING PDO</title>

        <meta charset="UTF-8">

        <meta name="viewport" content="width=device-width, initial-scale=1.0">

    </head>
    <body>
        <form action="updating.php" method="post">
    <input type="text" name="id"  placeholder="Enter new ID"><br><br>
    <input type="text" name="fname"  placeholder="Enter new First Name"><br><br>
    <input type="text" name="lname"  placeholder="Enter new Last Name"><br><br>
    <input type="number" name="age"  placeholder="Enter new age" min="13" max="90"><br><br>
    <input type="text" name="country"  placeholder="Enter new Nationality"><br><br>
    <input type="number" name="phone"  placeholder="Enter new Phone Number"><br><br>
    <input type="text" name="email"  placeholder="Enter new Email"><br><br>
    <input type="submit" name="update" value="update">
    </form>

    </body>

</html>

Answer 2

public class SpecialSeries {
    public static double SumOfSeries(double x, int numTerms) {
        if (numTerms == 1) {
            return x;
        }
        int maxOdd = numTerms * 2 - 1;
        int maxEven = numTerms * 2 - 2;
        double powerTerm = Math.pow(x, maxOdd) / maxOdd;
        int numerator = 1;
        for (int numMult = maxOdd - 2; numMult > 2; numMult -= 2) {
            numerator *= numMult;
        }
        int denominator = 2;
        for (int numMult = maxEven; numMult > 2; numMult -= 2) {
            denominator *= numMult;
        }
        return powerTerm * numerator / denominator + sumOfSeries(x, numTerms - 1);
    }

    public static void main(String[] args) {
        try {
            int numTerms = Integer.parseInt(args[0]);
            double x = Double.parseDouble(args[1]);
            System.out.println(sumOfSeries(x, numTerms));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

Answer 3

数学内容

首先让我们查看你的系列：所以你的系列可以表示如下：用：

现在，我们可以进行更多的数学简化，或继续进行实施

Java implimenttion

 public class SpecialSeries {

    public static double sumOfSeries(double x, int numTerms){
        double sum = x;
        //System.out.println("u["+0+"] = "+x);
        for (int k = 1; k < numTerms; k++) {
            double uk = Math.pow(x,2*k+1)/(double)(2*k+1);
            for (int i = 2*k-1; i >0; i-=2) {
                uk *= i/(double)(i+1);
            }
            //System.out.println("u["+k+"] = "+uk);
            sum += uk;
        }        
        return sum;
    }  

    public static void main(String[] args) {
        System.out.println(sumOfSeries(1, 5));
    }
 }

计算系列的总和

3 个答案: