二分查找java代码实现_二分查找java关键代码

public static void main(String[] args) {
		Integer[] arr =  new Integer[]{12,15,20,36,45,66,72,81,90};
		int des = 22;
		int search = binarySearch(arr, des);
		System.out.println(search);
		int recursive = binarySearchRecursive(arr, 0 , arr.length-1 ,des);
		System.out.println(recursive);
	}
	
	/**
	 * 二分查找 非递归  如果数组中不存在要查询的数返回-1
	 * 
	 * @param arr
	 * @param des
	 * @return
	 */
	public static int binarySearch(Integer[] arr, int des){
		int start = 0;
		int end = arr.length-1;
		
		while (start <= end) {
			int middle = (( end - start )>>1)+ start;
			if (des == arr[middle]) {
				return middle+1;
			}else if (des < arr[middle]) {
				end = middle-1;
			}else if (des > arr[middle]) {
				start = middle+1;
			}
		}
		return -1;
	}
	
	/**
	 * 二分查找 递归方式 如果数组中不存在要查询的数返回-1
	 * 
	 * @param args
	 * @param des
	 * @return
	 */
	public static int binarySearchRecursive(Integer[] args ,int start, int end, int des){
		int middle = -1;
		if (start <= end) {
			middle = (start + end) >> 1;
			if (des == args[middle]) {
				return middle+1;
			}else if (des < args[middle]) {
				end = middle -1;
				return binarySearchRecursive(args, start, end, des);
			}else if (des > args[middle]) {
				start = middle +1;
				return binarySearchRecursive(args, start, end, des);
			}
		}
		return middle;
	}