BubbleSort

sirin sevinc — Sun, 17 Feb 2008 20:37:23 +0000

Bubble sort has best-case complexity O(n). When a list is already sorted, bubblesort will pass through the list once, and find that it does not need to swap any elements. Thus bubblesort will make only n comparisons and determine that list is completely sorted. It will also use considerably less time O(n²) than if the elements in the unsorted list are not too far from their sorted places.



public class BubbleSort {

int[] data;

public BubbleSort(int[] data) {

super();

this.data = data;

}

public int[] sort() {

boolean isSwap = false;

int temp = 0;

do {

isSwap = false;

for (int i = 0; i  data[i + 1]) {

temp = data[i];

data[i] = data[i + 1];

data[i + 1] = temp;

isSwap = true;

}

}

} while (isSwap);

return data;

}

/**

* instead of doing n2 comparisons (and swaps), we can use only

* n + (n-1) + (n-2) + ... + 1 comparisons.

* This sums up to n(n + 1) / 2, which is still

* O(n²), but which can be considerably faster in practice.

*

* @return sorted data

*/

public int[] optimezedSort() {

boolean isSwap = false;

int temp = 0;

int n = data.length - 1;

do {

isSwap = false;

n = n - 1;

for (int i = 0; i  data[i + 1]) {

temp = data[i];

data[i] = data[i + 1];

data[i + 1] = temp;

isSwap = true;

}

}

} while (isSwap);

return data;

}

public static void main(String[] args) {

     int[] data = new int[] {1,2,3,4,5,8,6,9,7};

     System.out.println(Arrays.toString(new BubbleSort(data).sort()));

     System.out.println(Arrays.toString(new BubbleSort(data).optimezedSort()));

    }

}

handy » BubbleSort

BubbleSort