二分查找

package com.test4;
/**
 * @author qingfeng
 * 功能：二分查找
 */
public class BinarySearch {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int[] arr = {2,7,56,78,22};
        BSearch bs = new BSearch();
        bs.search(0, arr.length-1, 78, arr);
    }

}
class BSearch
{
    //key为待查找的值
    public void search(int leftIndex, int rightIndex,int key,int arr[])
    {
        if(leftIndex <= rightIndex)//递归条件
        {
            int mid = (leftIndex+rightIndex)/2;//找到中值
            {
                if(key == arr[mid])
                {
                    System.out.println("要找的值位置为"+mid);
                }
                else if(key < arr[mid])
                {
                    search(leftIndex,mid-1,key,arr);
                }
                else if(key > arr[mid])
                {
                    search(mid+1,rightIndex,key,arr);
                }
            }    
        }
    }
}