Java二分查找

    public static int binarySearch(int[] arr, int num) {
        //给定一个有序整型数组, 实现二分查找
        int low = 0;
        int high = arr.length - 1;
        while(low <= high){
            int mid = (low + high) / 2;
            if(arr[mid] > num){
                high = mid - 1;
            }else if(arr[mid] < num){
                low = mid + 1;
            }else{
                return mid;
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        int[] arr = {1,2,3,4,5,6,7,8,9};
        System.out.println(binarySearch(arr, 7));
        System.out.println(binarySearch(arr, 0));
    }

输出结果：