Java-数据结构与算法-二分查找法

1.二分查找法思路：不断缩小范围，直到low <= high

2.代码：

 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 }

3.结果：6