二分查找算法-Java

/**
 * @author cnkeysky
 */
public class DemoTest {

    public static void main(String[] args) {
        int[] arr = {1, 3, 10, 17, 20};
        int index = binarySearch(arr, 3);
        if (index < 0) {
            System.out.println("未查找到该数");
        } else {
            System.out.println("该数在数组中的下标为: " + index);
        }
    }

    public static int binarySearch(int[] arr, int value) {
        int len = arr.length;
        return binarySearch(arr, value, 0, len - 1);
    }

    public static int binarySearch(int[] arr, int value, int left, int right) {
        if (left > right) {
            return -1;
        }
        int mid = (right + left) / 2;
        if (arr[mid] == value) {
            return mid;
        } else if (arr[mid] < value) {
            return binarySearch(arr, value, mid + 1, right);
        } else {
            return binarySearch(arr, value, left, mid - 1);
        }
    }
    
}

来源：CSDN

作者：cnkeysky

链接：https://blog.csdn.net/cnkeysky/article/details/104451306