How Can I Convert Quicksort from Java to C++?

[needOfHelpCMath]

I have never done Java but my professor says it is similar to c++. I am trying to convert quicksort in java and covert it to c++.
I don't know if this is correct or not. Here is the code my professor gave us.

 .....Java......

public static void quicksort(char[], int left, int right) 
{
    int i, j;
    i - left; j - right;
    x = items[(left+right) / 2];

do
{
    while([items[i] < x) && (i <right)] i++;
    while[(x < items[j]) && (i > left)] j--;

    if (i <= j) {
       y = items[i];
       items[i] = items[j];
       items[j] = y;
       i++; j--; }
}
    while(i<=j);
    if (left < j) quicksort(items, left, j);
    if (i < right)quicksort(items,i,right);
    }

 ......C++......

void QuickSort(int[] nums, int left, int right) {
	int i, j,;
	int x, y;
	i - left;
	j-right;
	x = nums[(left+right)/2];
	
	while(nums[i] < x && i < right) {
		++i;
		while(x < num[j] && j > left) {
			j--;
			
			if(i <= j) {
				y = nums[i];
				nums[i] = nums[j];
				nums[j] = y;
				i++; j--;
			}
			}
		}
		}
	
	while(i <= j) {
		if(left < j) {
			QuickSort(nums, left);
		}
		if(i < right) {
			QuickSort(nums,i,right);
		}
	}

 

[johng1]

I assume your instructor gave you correct Java code and you didn't faithfully copy his code. Here's his correct quicksort:

   public static void quicksort(char[] items, int left, int right) {
      int i, j;
      i = left;
      j = right;
      char x = items[(left + right) / 2], y;
      do {
         while ((items[i] < x) && (i < right)) {
            i++;
         }
         while ((x < items[j]) && (j > left)) {
            j--;
         }
         if (i <= j) {
            y = items[i];
            items[i] = items[j];
            items[j] = y;
            i++;
            j--;
         }
      } while (i <= j);
      if (left < j) {
         quicksort(items, left, j);
      }
      if (i < right) {
         quicksort(items, i, right);
      }
   }

One small difference between Java and C++, Java arrays are declared with type[] name, but C++ arrays are type name[]. Example: Java char[] items in C++ is char items[]. One other small difference: Java allows you to declare variables anyplace before they are used. You should know about the do/while loop in C++ so a C++ implementation should be almost immediate.

FYI: There are many different ways to write quicksort. The given implementation is certainly correct and easy, but there are much better implementations. The wikipedia article https://en.wikipedia.org/wiki/Quicksort may be a little advanced, but it's pretty good.

 

[needOfHelpCMath]

I assume your instructor gave you correct Java code and you didn't faithfully copy his code. Here's his correct quicksort:

   public static void quicksort(char[] items, int left, int right) {
      int i, j;
      i = left;
      j = right;
      char x = items[(left + right) / 2], y;
      do {
         while ((items[i] < x) && (i < right)) {
            i++;
         }
         while ((x < items[j]) && (j > left)) {
            j--;
         }
         if (i <= j) {
            y = items[i];
            items[i] = items[j];
            items[j] = y;
            i++;
            j--;
         }
      } while (i <= j);
      if (left < j) {
         quicksort(items, left, j);
      }
      if (i < right) {
         quicksort(items, i, right);
      }
   }

One small difference between Java and C++, Java arrays are declared with type[] name, but C++ arrays are type name[]. Example: Java char[] items in C++ is char items[]. One other small difference: Java allows you to declare variables anyplace before they are used. You should know about the do/while loop in C++ so a C++ implementation should be almost immediate.

FYI: There are many different ways to write quicksort. The given implementation is certainly correct and easy, but there are much better implementations. The wikipedia article https://en.wikipedia.org/wiki/Quicksort may be a little advanced, but it's pretty good.

Thanks! that will help me alot. Appreciate it

 

[Evgeny.Makarov]

One small difference between Java and C++, Java arrays are declared with type[] name, but C++ arrays are type name[]. Example: Java char[] items in C++ is char items[].

And it is still possible to use C++ array syntax in Java as well.

One other small difference: Java allows you to declare variables anyplace before they are used.

Is it different in C++?

Your Java program compiles as a C++ program if one changes the array declaration and the method declaration. So in this example Java and C++ are basically the same.