有15个数已按由大到小的顺序存放在一个数组中，现再输入一个数，要求用折半查找法找出该数是数组中第几个元素的值。如果该数不在数组中，则打印出“无此数”*/-There are 15 numbers in ascending order has been placed in an array, now and then enter a number, asked to use a binary search method to find the number of elements in the a