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：

 package Test;

 import java.util.Arrays;

 public class BinarySearch {

     public static void main(String[] args) {
         int [] a = {1,5,7,9,11,12,16,20};
         int target = 16;
         //System.out.println(Arrays.binarySearch(a, target));
         System.out.println(binarySearch(a, target));
     }

     public static int binarySearch(int [] a, int target){
         int low = 0;
         int high = a.length - 1;

         while (low <= high) {
             int mid = (low + high) >>> 1;
             int midVal = a[mid];

             if (midVal < target)
                 low = mid + 1;
             else if (midVal > target)
                 high = mid - 1;
             else
                 return mid; // key found
         }
         return -(low + 1);  // key not found.
     }
 }

3.结果：6