二進制到十進制轉換Java代碼錯誤

Question

所以我正在做一個項目，我必須做從二進制數轉換爲小數等。 這是我的代碼到目前爲止，還有一個錯誤。在一個二進制數字如1101中，假設出來的十進制數字是13，但從代碼中出來的數字是11.這個錯誤發生在所有以一堆1開始並且像單個0開始的二進制數字上。

import java.util.*; // imports everything in java.util 

public class newCalculator{ 

    * Conversion asks the user for a binary number. It converts the input to a decimal number 
    * using arrays and then displays the answer to the screen. 
    */ 

    public static void main (String[]args){ // creates the main method 
    binaryToDecimal(); //calls the user defined method binaryToDecimal 
    } 

    public static void binaryToDecimal() { 
    Scanner scan = new Scanner(System.in); // Creates a new Scanner 
    System.out.println("Input a Binary Number"); // Asks the user to input their number 
    String binary = scan.next(); // Creates a new String that stores the value of the input 
    char[] charArray = binary.toCharArray(); //Create a new Array and implements in the input 
    double answer = 0; // Creates a new double called answer setting it to zero 
    for (double index = 0; index < charArray.length; index++){//For loop 
     if (charArray[(int)index] == '1') {//If statement that allows the binary input to work 
     answer = answer + Math.pow(2.0, index);//Sets the answer with the math class power of 2 
     } 
    } 
    System.out.println(answer);//Prints out the final conversion result 
    /* Test Cases Expected Result Output 
    * 101     5    5 
    * 11     3    3 
    * 1     1    1 
    * 1101    13   11<-- 
    * 111     7    7 
    * 1000001    65   65 
    * 1111    15   15 
    * 1001    9    9 
    * 11101    29   23<-- 
    * 10101    21   21 
    * 
    */ 
    } 

} 

Answer 1

正在計算您的預期結果，就好像從右向左讀取二進制字符串一樣;但是，您的代碼正在從左到右讀取二進制字符串。

更改此：

for (double index = 0; index < charArray.length; index++){ 

要這樣：

for (double index = charArray.length - 1; index >= 0; index--) { 

你也應該改變使用整數作爲索引，這樣的：

for (int index = charArray.length - 1; index >= 0; index--) { 

Answer 2

你正在經歷你的位錯誤順序。你的第一個索引指的是最重要的位，而不是最低位。

您對Math.pow調用應該是

answer = answer + Math.pow(2.0, (charArray.length - index - 1)); 

正如湯姆·利斯已經指出的那樣，請使用您的循環指數的整數。

Answer 3

對稱是答案。如果你看看所有的測試輸入，它們都是對稱的，除了1101

你的算法是，與其index在Math.pow你需要使用Math.pow(2.0, charArray.length - i - 1)異常正確的，下面是正確執行（實際上只是小的增量變化）

import java.util.Scanner; 

public class NewCalc { 

    public static void main(String[] args) { 
     binaryToDecimal(); 
    } 

    public static void binaryToDecimal() { 
     Scanner scan = new Scanner(System.in); 
     System.out.println("Input a Binary Number"); 
     String binary = scan.next(); 
     char[] charArray = binary.toCharArray(); 
     double answer = 0; 
     for (int i = 0; i < charArray.length; i++) { 
      answer = charArray[i] == '1' 
        ? answer + Math.pow(2.0, charArray.length - i - 1) 
        : answer; 
     } 
     System.out.println(answer); 
    } 
} 

Answer 4

package pdaproject; 
import java.util.Scanner; 
public class NewCalc { 

    public static void main(String[] args) { 
     binaryToDecimal(); 
    } 
    // convert to decimal (base 10) 
    public static void binaryToDecimal() { 
     Scanner scan = new Scanner(System.in); 
     System.out.println("Input a Binary Number"); 
     String binary = scan.next(); 
     int answer = 0; 
     // process left to right 
     for (int i = 0; i < binary.length(); i++) { 
      answer = 2 * answer + (binary.charAt(i) == '1' ? 1 : 0); 
     } 
     System.out.println(answer); 
    } 
} 

Answer 5

public class BinaryToDecimal { 
    static int testcase1=1001; 
    public static void main(String[] args) { 
     BinaryToDecimal test = new BinaryToDecimal(); 
     int result = test.convertBinaryToDecimal(testcase1); 
     System.out.println(result); 
    } 

    //write your code here 
    public int convertBinaryToDecimal(int binary) 
    { 
     int deci = 0; 
     int p=1; 
     int rem = 0; 
     while(binary>0) 
     { 
      rem = binary%10; 
      deci = deci+(rem*p); 
      p = p*2; 
      binary = binary/10; 
     } 

     return deci; 
    } 

}