二分查找法

代码如下：

public class BinarySearch {
    /*
     * 循环实现二分查找算法arr 已排好序的数组x 需要查找的数-1 无法查到数据
     */
    public static int binarySearch(int[] arr, int x) {
        int low = 0;
        int high = arr.length-1;
        while(low <= high) {
            int middle = (low + high)/2;
            if(x == arr[middle]) {
                return middle;
            }else if(x <arr[middle]) {
                high = middle - 1;
            }else {
                low = middle + 1;
            }
        }
        return -1;
    }
    //递归实现二分查找
    public static int binarySearch(int[] dataset,int data,int beginIndex,int endIndex){
        int midIndex = (beginIndex+endIndex)/2;
        if(data <dataset[beginIndex]||data>dataset[endIndex]||beginIndex>endIndex){
            return -1;
        }
        if(data <dataset[midIndex]){
            return binarySearch(dataset,data,beginIndex,midIndex-1);
        }else if(data>dataset[midIndex]){
            return binarySearch(dataset,data,midIndex+1,endIndex);
        }else {
            return midIndex;
        }
    }

    public static void main(String[] args) {
        int[] arr = { 6, 12, 33, 87, 90, 97, 108, 561 };
        System.out.println("循环查找：" + (binarySearch(arr, 87)));
        System.out.println("递归查找："+binarySearch(arr,87,0,arr.length-1));
    }
}