如何调试不能按预期工作的switch语句？

Question

I have to segregate 0s and 1s within same array. I have written the logic, but not getting proper output. Can you please check the code and let me know what is the mistake.

package Segregate;

public class Segregate {

    public void segregate0and1(int arr[], int arr_size){

        int i=0;
        int j=arr_size-1;
        while(j>=i){
            switch(arr[i]){
            case 0:{
                i++;
            }
            case 1: {


                int temp = arr[i];
                arr[i] = arr[j];
                arr[j] = temp;
                j--;

         }
            }

        }

    }

    public static void main(String[] args) {
        Segregate seg = new Segregate ();
        int arr[] = {0, 1, 0, 1, 0,0,1};
        int arr_size = arr.length;
        seg.segregate0and1(arr, arr_size);

        System.out.print("Array after segregation is ");
        for (int k = 0; k < arr_size; k++){
            System.out.print(arr[k] + " ");
        }
    }

}

Answer 1

I would suggest to sort the array instead of complicating the code and logic

  public static void main(String[] args) {
    int arr[] = { 0, 1, 0, 1, 0, 0, 1 };
    Arrays.sort(arr);
    System.out.println(Arrays.toString(arr));

    }

Answer 2

Better way of doing things. Click Here for src.

Replace this

 public void segregate0and1(int arr[], int arr_size){

    int i=0;
    int j=arr_size-1;
    while(j>=i){
        switch(arr[i]){
        case 0:{
            i++;
        }
        case 1: {


            int temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
            j--;

     }
        }

    }

}

Replace with this

void segregate0and1(int arr[], int size) 
{
    /* Initialize left and right indexes */
    int left = 0, right = size - 1;

    while (left < right) 
    {
        /* Increment left index while we see 0 at left */
        while (arr[left] == 0 && left < right)
           left++;

        /* Decrement right index while we see 1 at right */
        while (arr[right] == 1 && left < right)
            right--;

        /* If left is smaller than right then there is a 1 at left
           and a 0 at right.  Exchange arr[left] and arr[right]*/
        if (left < right) 
        {
            arr[left] = 0;
            arr[right] = 1;
            left++;
            right--;
        }
    }
}

Answer 3

The break statement is missing in the switch-case-construct. It should be similar to this: (I also included the default for completeness).

public void segregate0and1(int arr[], int arr_size){
  int i=0;
  int j=arr_size-1;
  while(j>=i){      
      switch(arr[i]){
      case 0:{
          i++;
          break;
      }
      case 1: {
        int temp = arr[i];
          arr[i] = arr[j];
          arr[j] = temp;
          j--;
          break;
      }
        default:
        //empty 
      }
  }
}

For testing I added a System.out.println right behind the while . The output is

stefan@mars:~$ java Segregate 
[0, 1, 0, 1, 0, 0, 1]
[0, 1, 0, 1, 0, 0, 1]
[0, 1, 0, 1, 0, 0, 1]
[0, 0, 0, 1, 0, 1, 1]
[0, 0, 0, 1, 0, 1, 1]
[0, 0, 0, 1, 0, 1, 1]
[0, 0, 0, 0, 1, 1, 1]

The last line contains the "sorted" array.