二分查找

二分查找

/**
 * 二分查找
 */
public class BinarySearch {
    public static void main(String[] args) {
        int[] arr = {12, 34, 45, 56, 67, 78, 89, 90, 99};
        System.out.println(getIndex(arr, 99));
    }
    public static int getIndex(int[] arr, int value){
        int low = 0;
        int high = arr.length-1;

        while(low<=high){
           int mid = (low + high)/2;
           if(arr[mid]>value){
               high = mid - 1;
           }else if (arr[mid]<value){
               low = mid + 1;
            }else{
               return mid;
           }
        }

        return -(low+1);
    }
}