public class Sort {
 
  /** Display the contents of the list. */
  public static void print(int[] list) {
    for (int i = 0; i < list.length; i++) {
      System.out.print(list[i] + " ");
    }
    System.out.println();
  }
  
  /**
   * Bubble sort:
   * 
   * - traverse the list comparing pairs of elements
   * - move the larger element into the higher position
   * - repeat list.length - 1 times
   */ 
  public static void bubbleSort(int[] list) {
    int comps = 0;
    int swaps = 0;
    
    for (int j = 0; j < list.length - 1; j++) {
      for (int i = 0; i < list.length - 1; i++) {
        
        // count the number of comparions
        comps++;
        
        // compare neighbouring elements
        if (list[i] > list[i + 1]) {
          
          // swap i with i + 1
          int temp = list[i];
          list[i] = list[i + 1];
          list[i + 1] = temp;
          
          // count the number of swaps
          swaps++;
        }
      }
    }
    
    print(list);
    System.out.println("Comparisons: " + comps 
                         + " Swaps: " + swaps);
  }
  
  /**
   * Improved bubble sort:
   *  - stop sorting when the array becomes sorted
   *  - do not compare elements of the array with
   *    the elements that are in their correct sorted
   *    position
   */ 
  public static void bubbleSort2(int[] list) {
    int comps = 0;
    int swaps = 0;
    boolean didSwap = true;
    
    // didSwap tracks whether any elements of the array
    // were swapped during the last iteration of the loop.
    // If no elements were swapped, the the array is 
    // sorted, so we can stop.
    for (int j = 0; j < list.length - 1 && didSwap; j++) {
      didSwap = false;
      
      // at this point, j elements are already in their
      // correct sorted position, so we do not compare
      // with the last j elements in the list
      for (int i = 0; i < list.length - 1 - j ; i++) {
        
        // count the number of comparions
        comps++;
        
        // compare neighbouring elements
        if (list[i] > list[i + 1]) {
          
          didSwap = true;
          
          // swap i with i + 1
          int temp = list[i];
          list[i] = list[i + 1];
          list[i + 1] = temp;
          
          // count the number of swaps
          swaps++;
        }
        
      }
    }
   
    print(list);
    System.out.println("Comparisons: " + comps 
                         + " Swaps: " + swaps);
  }
  
}