java 复习003 之排序篇

由java 复习003跳转过来的
C语言实现版见some-sort-algorithms

1. 快速排序（不稳定 O(n log n)）

   package vell.bibi.sort_algorithms;
   
   import vell.bibi.sort_algorithms.util.vell001;
   
   public class QuickSort {
   
       public static int partition(int[] a, int low, int high){
           int cup;
           cup = a[low]; // 保存关键字
           while(high > low){
               while(high > low && a[high] >= cup) high--; // 由high开始找，找到小于关键字的位置 
               a[low] = a[high];
               while(high > low && a[low] <= cup) low ++; // 由low开始找，找到大于关键字的位置
               a[high] = a[low];
           }
           a[low] = cup;
           return low;
       }
       
       public static void sort(int[] a, int low, int high){
           if(high <= low) return;
           int mid = partition(a, low, high); // 分成两个区
           sort(a, low, mid-1);
           sort(a, mid+1, high);
       }
       
       public static void main(String[] args) {
           int[] a = vell001.getRandomList(10, 100);
           vell001.printList(a);
           sort(a, 0, a.length-1);
           vell001.printList(a);
       }
   }

2. 冒泡排序 （稳定 O(n2)）

   package vell.bibi.sort_algorithms;
   
   import vell.bibi.sort_algorithms.util.vell001;
   
   public class BubbleSort {
   
       public static void sort(int[] a){
           int i, j, cup;
           boolean flag;
           for(i=a.length, flag=true; flag && i>0; i--){
               flag = false;
               for(j=0; j<i-1; j++){
                   if(a[j] > a[j+1]){
                       cup = a[j];
                       a[j] = a[j+1];
                       a[j+1] = cup;
                       flag = true;
                   }
               }
           }
       }
       
       public static void main(String[] args) {
           int[] a = vell001.getRandomList(10, 100);
           vell001.printList(a);
           sort(a);
           vell001.printList(a);
       }
   
   }

3. 希尔排序（不稳定 O(n log n)）

   package vell.bibi.sort_algorithms;
   
   import vell.bibi.sort_algorithms.util.vell001;
   
   public class ShellSort {
       
       public static void sort(int[] a){
           int i, j, d, cup;
           for(d=a.length/2; d>0; d=d/2){
               for(i=d; i<a.length; i++){
                   cup = a[i];
                   for(j=i-d; j>=0 && a[j]>cup; j=j-d){
                       a[j+d] = a[j];
                   }
                   a[j+d] = cup;
               }
           }
       }
       
       public static void main(String[] args) {
           int[] a = vell001.getRandomList(10, 100);
           vell001.printList(a);
           sort(a);
           vell001.printList(a);
       }
   
   }

4. 堆排序（不稳定 O(n log n)）

   package vell.bibi.sort_algorithms;
   
   import vell.bibi.sort_algorithms.util.vell001;
   
   public class HeapSort {
   
       public static void heapAdjust(int[] a, int father, int length){
           int child, cup;
           for(child=father*2+1, cup=a[father]; child<length; father=child, child=father*2+1){
               if(child+1 < length && a[child+1] > a[child])
                   child ++;
               if(a[child] > cup){
                   a[father] = a[child];
                   a[child] = cup;
               } else
                   break;
           }
       }
       
       public static void sort(int[] a){
           int cup;
           for(int i=a.length/2; i>=0; i--){
               heapAdjust(a, i, a.length);
           }
           
           for(int i=a.length-1; i>0; i--){
               cup = a[0];
               a[0] = a[i];
               a[i] = cup;
               heapAdjust(a, 0, i);
           }
       }
       
       public static void main(String[] args) {
           int[] a = vell001.getRandomList(10, 100);
           vell001.printList(a);
           sort(a);
           vell001.printList(a);
       }
   
   }

5. 归并排序（稳定 O(n log n) 需要O(n)额外空间）

   package vell.bibi.sort_algorithms;
   
   import vell.bibi.sort_algorithms.util.vell001;
   
   public class MergeSort {
       
       public static void merge(int[] a, int low, int mid, int high){
           int i=low, j=mid, k=0;
           int[] cup = new int[high-low];
           while(i<mid && j<high){
               if(a[i] <= a[j])
                   cup[k++] = a[i++];
               else
                   cup[k++] = a[j++];
           }
           while(i<mid) cup[k++] = a[i++];
           while(j<high) cup[k++] = a[j++];
           
           for(k=0; k<cup.length; k++){
               a[low + k] = cup[k];
           }
       }
       
       public static void sort(int[] a, int low, int high){
           if(high - low <= 1) return;
           int mid = (high + low) / 2;
           sort(a, low, mid);
           sort(a, mid, high);
           merge(a, low, mid, high);
       }
   
       public static void main(String[] args) {
           int[] a = vell001.getRandomList(10, 100);
           vell001.printList(a);
           sort(a, 0, a.length);
           vell001.printList(a);
       }
   
   }

6. vell001.java (我的小工具库)

   package vell.bibi.sort_algorithms.util;
   
   public class vell001 {
       
       public static void printList(int[] a){
           for(int i=0; i<a.length; i++){
               System.out.print(a[i] + "  ");
           }
           System.out.println();
       }
       
       public static int[] getRandomList(int n, int max){
           int[] a = new int[n];
           for(int i=0; i<n; i++){
               a[i] = (int)(Math.random() * max);
           }
           return a;
       }
   }

原文地址: http://vview.ml/2014/04/13/some-sort-algorithms-java.html
written by Vell Bibi posted at VBlog