java 冒泡排序及其改进

http://blog.csdn.net/tjunxin/article/details/8711389

 

冒泡排序经典算法：

 

public class HelloWorld {

         staticfinal int SIZE=10;

         publicstatic void bubbleSort(int[] a) {

                    int temp;

                    for (int i = 1; i < a.length; i++) {

              //将相邻两个数进行比较，较大的数往后冒泡

                  for (int j = 0; j < a.length - i; j++) {

                            if (a[j] > a[j + 1]) {

                   //交换相邻两个数

                                     temp=a[j];

                                     a[j]=a[j+1];

                                     a[j+1]=temp;

                            }

                  }

                  System.out.print("第"+i+"步排序结果:");                   //输出每步排序的结果

                  for(int k=0;k

                  {

                            System.out.print(" "+a[k]); // 输出

                  }

                  System.out.print("\n");

                    }

          }

 

         publicstatic void main(String[] args) {

                   int[]shuzu=new int[SIZE];

                   inti;

                   for(i=0;i

                   {

                            shuzu[i]=(int)(100+Math.random()*(100+1));                            //初始化数组

                   }

                   System.out.print("排序前的数组为：\n");                               //输出排序前的数组

                   for(i=0;i

                   {

                            System.out.print(shuzu[i]+"");

                   }

                   System.out.print("\n");

                   bubbleSort(shuzu);                                       //排序操作

                   System.out.print("排序后的数组为：\n");

                   for(i=0;i

                   {

                            System.out.print(shuzu[i]+"");                                             //输出排序后的数组

                   }

                   System.out.print("\n");

 

         }

}

存在问题：

         每次必须排序n-1次，若存在i（i

 

改进一：

         设置标记符号，退出循环。

for (int i = 1; i < a.length; i++) {

              //将相邻两个数进行比较，较大的数往后冒泡

                              boolean h=false;

                  for (int j = 0; j < a.length - i; j++) {

                            if (a[j] > a[j + 1]) {

                   //交换相邻两个数

                                     temp=a[j];

                                     a[j]=a[j+1];

                                     a[j+1]=temp;

                                     

                                     h=true;

                            }

                  }

                  

                  if(!h)

                             break;

 

 

改进二：

         在改进一的基础确定排序位置

int b=0;

                    int c=0;

          for (int i = 1; i < a.length; i++) {

              //将相邻两个数进行比较，较大的数往后冒泡

                           b=c;

                  for (int j = a.length-i; j>b ; j--) {

                            if (a[j] < a[j - 1]) {

                   //交换相邻两个数

                                     temp=a[j];

                                     a[j]=a[j-1];

                                     a[j-1]=temp;

                                     c=j;

                            }

                  }

                  

                  if(b==c)

                            break;