二分查找or折半查找

 1 package com.gxf.search;
 2 
 3 /**
 4  * 测试折半查找or二分查找
 5  * @author xiangfei
 6  *
 7  */
 8 public class BiSearch {
 9     
10     /**
11      * 非递归实现,从第1个元素开始查找
12      * @param array
13      * @param k
14      * @return 0 查找失败
15      */
16     public int biSearch(int array[], int k){
17         int low = 1;
18         int high = array.length - 1;
19         
20         while(low <= high){
21             int mid = (low + high) / 2;
22             if(k == array[mid]){
23                 return mid;
24             }
25             if(k > array[mid]){
26                 low = mid + 1;                
27             }
28             else{
29                 high = mid - 1;
30             }
31         }
32         return 0;
33     }
34     
35     /**
36      * 递归实现
37      * @param array
38      * @param k
39      * @param l
40      * @param h
41      * @return
42      */
43     public int biSearch(int array[], int k, int l, int h){
44         if(l > h){
45             return 0 ;
46         }
47         if(k == array[(l + h) / 2])
48             return (l + h) / 2;
49         else if(k > array[(l + h) / 2]){
50             return biSearch(array, k, (l + h) / 2 + 1, h);
51         }
52         else{
53             return biSearch(array, k, l, (l + h) / 2 - 1);
54         }
55     }
56 
57     public static void main(String[] args) {
58         BiSearch biSearch = new BiSearch();
59         int array[] = {0,1,3,4,5,6,7};
60         System.out.println(biSearch.biSearch(array, 5));
61         System.out.println(biSearch.biSearch(array, 5, 1, array.length - 1));
62 
63     }
64 
65 }