最大堆

Posted 2020-07-23

二叉堆：

　　堆排序时间复杂度O(nlgn)

 1 package com.bing;
 2 
 3 import java.util.Arrays; 
 4 //ywb
 5 public class HeapSort {
 6     
 7     
 8     //首先假设 以left(i) ,right(i) 为根节点的子树满足最大堆性质
 9     public static  <T extends Comparable<? super T>> void  max_HeapIf_Y(T[] A,int i,int heapSize)
10     {
11         int l=left(i),r=right(i),largest;
12         if(l<=heapSize && A[i].compareTo(A[l])<0)
13         {
14             largest = l;
15         }else
16         {
17             largest = i;
18         }
19         if(r<=heapSize && A[largest].compareTo(A[r])<0)
20         {
21             largest = r;
22         }
23         if(largest!=i)
24         {
25             exchange(A,i,largest);
26             max_HeapIf_Y(A,largest,heapSize);
27         }
28         
29     }
30     
31     public static <T extends Comparable<? super T>> void build_max_heap(T[] A,int heapSize) 
32     {
33         
34         for(int i=A.length/2;i>=0;i--)
35         {
36             max_HeapIf_Y(A,i,heapSize);
37         }
38     }
39     
40     public static <T extends Comparable<? super T>> void heapSort(T[] A) 
41     {
42         build_max_heap(A,A.length-1);
43         int heapSize = A.length-1;
44         for(int i=A.length-1;i>=1;i--)
45         {
46             exchange(A,0,i);
47             heapSize--;
48             max_HeapIf_Y(A,0,heapSize);
49         }
50     }
51     public static void main(String[] args) {
52         Integer[] a = {8,9,6,3,7,0,2,15,-1,8,8,28,4,0,45,78,22
53                 ,2000,3243,4,0,4,4,48,3,33,55,11,22,9};
54         System.out.println(Arrays.toString(a));
55         long start = System.nanoTime();
56         heapSort(a);
57         long end = System.nanoTime();
58         System.out.println(Arrays.toString(a));
59         System.out.println(end - start);
60         
61     }
62     public static int left(int i)
63     {
64         return 2*i+1;    
65     }
66     public static int right(int i)
67     {
68         return 2*i+2;    
69     }
70     public static int parent(int i)
71     {
72         return i/2;    
73     }
74     public static <T> void exchange(T[] A,int i,int j){
75         T temp = A[i];
76         A[i] = A[j];
77         A[j] = temp;
78     }
79     
80 }

 

　

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