Java-数据结构与算法-二分查找法

 1 package Test;
 2 
 3 import java.util.Arrays;
 4 
 5 public class BinarySearch {
 6     
 7     public static void main(String[] args) {
 8         int [] a = {1,5,7,9,11,12,16,20};
 9         int target = 16;
10         //System.out.println(Arrays.binarySearch(a, target));
11         System.out.println(binarySearch(a, target));
12     }
13 
14     public static int binarySearch(int [] a, int target){
15         int low = 0;
16         int high = a.length - 1;
17 
18         while (low <= high) {
19             int mid = (low + high) >>> 1;
20             int midVal = a[mid];
21 
22             if (midVal < target)
23                 low = mid + 1;
24             else if (midVal > target)
25                 high = mid - 1;
26             else
27                 return mid; // key found
28         }
29         return -(low + 1);  // key not found.
30     }
31 }