如何在java中找到for循環中的最佳對

Question

import java.util.Scanner; 
public class ContainerCalculator { 

    public static void main(String[] args) { 

      Scanner scnr = new Scanner(System.in); 

      //Print the Welcome message 
      System.out.println("Welcome to the Container Calculator!"); 
      System.out.println("===================================="); 

      //Set the value that users just input to height 


      //Variable Declaration 

      //Declare the diameter of a cylinder 
      float d = 0; 
      //Declare the height of a cylinder 
      float h = 0; 
      //Declare the volume of a cylinder 
      float v = 0; 
      //Declare the surface are of a cylinder 
      float s = 0; 



      //Set the value that users just input to diameter 

      //Ask users to input the diameter and height of a cylinder 

      System.out.print("Enter the diameter of a cylinder (in centimeters): "); 
      boolean validDiameter = false; 
      do { 
        if (scnr.hasNextInt()){ 
          d = scnr.nextInt(); 
          if (d <= 0) { 
            System.out.print("Please enter a positive integer value: "); 
          } 
          else { 
          validDiameter = true; 
        } 
      } 
        else { 
          System.out.print("Please enter an integer value (less than 2,147,483,648) as decimal digits: "); 
          scnr.nextLine(); 
        } 
      } while (!validDiameter); 



      System.out.print("Enter the height of a cylinder (in centimeters): "); 
      boolean validHeight = false; 
      do { 
        if (scnr.hasNextInt()){ 
          h = scnr.nextInt(); 
          if (h <= 0) { 
            System.out.print("Please enter a positive integer value: "); 
          } 
          else { 
          validHeight = true; 
        } 
        } 
        else { 
          System.out.print("Please enter an integer value (less than 2,147,483,648) as decimal digits: "); 
          scnr.nextLine(); 
        } 
      } while (!validHeight); 



      //Calculate the value of volume and surface area of the cylinder 
      v = (float) ((h*Math.PI*d*d)/4.0); 
      s = (float) ((Math.PI*d*d/2 + d*Math.PI*h)); 

      //Print the value of volume 

      System.out.println("A can with a diameter of " + d+ " and a height of "+ h+ " has "); 
      //Print with only two places to the right of the decimal 
      System.out.printf("\ta volume of %.2f", v); 
      System.out.println(","); 

      //Print the value of surface area 

      //Print with only two places to the right of the decimal 
      System.out.printf("\tand a surface area of %.2f", s); 
      System.out.println("."); 



      double newVolume ; 
      double newSurface ; 
      double bestVolume = 0; 
      double bestSurface = 0; 
      double newD = 0; 
      double newH = 0; 
      double bestD = 0; 
      double bestH = 0;    

      for (newD = 1.0; newD <= v; newD++) { 
        for (newH = 1.0; newH <= v; newH++){ 

          newVolume = (float) ((newH*Math.PI*newD*newD)/4.0); 
          newSurface = (float) ((Math.PI*newD*newD/2 + newD*Math.PI*newH)); 

           if (newVolume > v && newSurface < s) 
          { 

            bestVolume = newVolume; 
            bestSurface = newSurface; 
            bestD = newD; 
            bestH = newH; 

          }  

        } 
        } 
      System.out.println("*** Surface Area Optimizer ***"); 

      System.out.println("A can with a diameter of " + bestD+ " and a height of "+ bestH+ " has "); 
      //Print with only two places to the right of the decimal 
      System.out.printf("\ta volume of %.2f", bestVolume); 
      System.out.println(","); 

      //Print the value of surface area 

      //Print with only two places to the right of the decimal 
      System.out.printf("\tand a surface area of %.2f", bestSurface); 
      System.out.println("."); 

      //Print the end message 
      System.out.println("============================================="); 
      System.out.println("Thank you for using the Container Calculator."); 
      } 



    } 

我想問一個關於for循環部分的問題。該部分的預期結果是打印出最小的表面積。例如，如果我在直徑（d）和高度（s）上輸入7，newDiameter應該是5，newheight應該是4，但是我的代碼只是輸出6和3.如何改進？

Answer 1

的問題是在這裏：if (newVolume > v && newSurface < s)

你試圖找到一種表面比上最好的面小，所以用這個條件來代替：if (newVolume >= v && newSurface < bestSurface)。

萬一進入h和d已經最優的，best*變量應該被初始化爲「原始」值，例如bestVolume = v。