具有四种颜色的荷兰国旗算法 [英] Dutch national flag algorithm with four colors

问题描述

我经历了两种和三种颜色的解决方案，但无法获得四种颜色的解决方案.

I went through a solution for two and three colors but I am unable to get it for four colors.

请帮助.

会是rrbb????yyyggg吗? 我们将如何交换绿色标志?

Will it be rrbb????yyyggg? How will we swap the green flag?

我尝试了以下解决方案，但无法将最后一个黄色替换为绿色.

I tried the solution below but it is not working with swapping the last yellow with green.

  public class count123 {

// Java program to sort an array of 0, 1 and 2,3

    static void sort0123(int a[], int arr_size)
    {
        int lo = 0;
        int hi = arr_size - 1;
        int mid = 0,temp=0;
        int h2=arr_size - 1;
        while (mid <= hi)
        {
            switch (a[mid])
            {
            case 0:
            {
                temp = a[lo];
                a[lo] = a[mid];
                a[mid] = temp;
                lo++;
                mid++;
                break;
            }
            case 1:
                mid++;
                break;
            case 2:
            {
                temp = a[mid];
                a[mid] = a[hi];
                a[hi] = temp;

                hi--;
                h2=hi;
                break;
            }
            case 3:{
                temp = a[mid];
                a[mid] = a[h2];
                a[h2] = temp;
            //  h2--;
                //hi=h2;
                break;

            }
            }
        }
    }

    /* Utility function to print array arr[] */
    static void printArray(int arr[], int arr_size)
    {
        int i;
        for (i = 0; i < arr_size; i++)
            System.out.print(arr[i]+" ");
            System.out.println("");
    }

    /*Driver function to check for above functions*/
    public static void main (String[] args)
    {
        int arr[] = {0, 1, 0,1,2,2,0,3,3,0,0,1};
        int arr_size = arr.length;
        sort0123(arr, arr_size);
        System.out.println("Array after seggregation ");
        printArray(arr, arr_size);
    }
}
/*This code is contributed by Devesh Agrawal*/

推荐答案

我运行您的代码，并意识到您的代码进入了无限循环，这使您的程序无能为力.

I run your code and realized that your code goes into infinite loop, which let does your programm do nothing.

在主方法中，调用了sort0123(arr, arr_size);，在此方法中，while (mid <= hi)，mid = 6和hi = 9，这意味着6 <= 9，并且由于该原因，由于以下事实，此条件无限地返回true总是在某些情况下转到情况3，而在情况3中，mid和hi的值不变.

In the main method, sort0123(arr, arr_size); is called and within this method, while (mid <= hi), mid = 6 and hi = 9 and that means 6 <= 9 and because of this resaon, this condition returns true infinitely because of the fact that it goes always to the case 3 at some point and in the case 3, the values of mid and hi are not changed.

为了能够运行您的代码，您应该在逻辑上更改mid和/或hi的值，并使用它来改变程序的行为.

In order to be able to run your code, you should change the value(s) of mid and/or hi logically and with it, your program can behave, how you wanted.

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