数据结构--排序之冒泡排序

数据结构–排序
可以通过理解各个排序算法的不变性来加深对算法的理解

冒泡排序BubbleSort
不变性:out右边的所有数据项都是有序的。out为outer loop外循环体中的变量。

The Point:

for (out = arrLen-1; out > 1; out--) { //outer loop backword
    for (in = 0; in < out; in++) { //inner loop forward
        if (a[in] > a[in+1]) {
            swap(in, in+1);
        }
    }
}

The Code:

public class BubbleSort {
    private static long[] a;

    public static void main(String[] args) {
        a = new long[]{88, 5, 44, 12, 15, 18, 0, 2};
        bubbleSort(a);//sorting and showing the orderly elements
    }

    //sorting
    private static void bubbleSort(long[] a){
        int out, in;
        int arrLen = a.length;
        display(a);//before sorting
        for (out = arrLen-1; out > 1; out--) { //outer loop backword
            for (in = 0; in < out; in++) { //inner loop forward
                if (a[in] > a[in+1]) {
                    swap(in, in+1);
                }
            }
        }
        display(a);//after sorting
    }

    //swap the elements
    private static void swap(int one, int two){
        long temp = a[one];
        a[one] = a[two];
        a[two] = temp;
    }

    //show the elements
    private static void display(long[] a){
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < a.length; i++) {
            sb.append(a[i] + " ");
        }
        System.out.println(sb.toString());
    }
}