Array resort of an in depth analysis of how to put all the odd Numbers in front of all the even Numbers

  • 2020-04-01 02:07:26
  • OfStack

Here is an efficient algorithm that can be implemented in order (n) time complexity.
The core idea is: Define two Pointers, one pointer A to scan from front to back and one pointer B to scan from back to back. Pointer A scans to an even number to pause, pointer B scans to an odd number to pause, and then exchanges the two Numbers. After the swap, continue to scan and swap as mentioned above, until pointer A and pointer B coincide to stop.
The Java code of this algorithm is as follows:

package Reorder;
public class Reorder {

 public static void main(String[] args) {
  int[] list = { 1, 2, 3, 4, 5, 7, 9, 11 };
  reorderOddEven(list);
 }
 public static void reorderOddEven(int[] list) {
  int length = list.length;
  for (int i = 0; i < length; i++) {
   System.out.print(list[i] + " ");
  }
  System.out.print("n");
  int begin = 0;
  int end = length - 1;
  while (begin < end) {
   while (begin < end && (list[begin] & 0x1) != 0)
    begin++;
   while (begin < end && (list[end] & 0x1) == 0)
    end--;
   if (begin < end) {
    int temp = list[begin];
    list[begin] = list[end];
    list[end] = temp;
   }
  }
  for (int i = 0; i < length; i++) {
   System.out.print(list[i] + " ");
  }
 }
}

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