Java实现二分查找递归和非递归

Java实现二分查找递归和非递归

public class Demo {

    public static void main(String[] args) {
        int[] arr={-1,0,3,5,9,12};//查找的数组
        int searchNum=13;//查找的目标数
        Arrays.sort(arr);

        int resultOne=binarySearchOne(arr,searchNum,0,arr.length-1);
        System.out.println(resultOne);

        int resultTwo=binarySearchTwo(arr,searchNum);
        System.out.println(resultTwo);
    }

    /**
     * 递归实现
     * @param arr
     * @param searchNum
     * @param start
     * @param end
     * @return
     */
    public static int binarySearchOne(int[] arr,int searchNum,int start,int end){
        if(start>end)
            return -1;
        int middle=(start+end)/2;
        if(searchNum<arr[middle])
            return binarySearchOne(arr,searchNum,start,middle-1);
        else if(searchNum>arr[middle])
            return binarySearchOne(arr,searchNum,middle+1,end);
        else
            return middle;
    }

    /**
     * 非递归实现
     * @param arr
     * @param searchNum
     * @return
     */
    private static int binarySearchTwo(int[] arr, int searchNum) {
        int start=0;
        int end=arr.length-1;
        while(start<=end){
            int middle=(start+end)/2;
            if(searchNum<arr[middle])
                end=middle-1;
            else if(searchNum>arr[middle])
                start=middle+1;
            else
                return middle;
        }
        return -1;
    }
}