有15个数按由大到小的顺序存放在一个数组中，输入一个数，要求用折半查找法找出该数是数组中的第几个元素的值。如果该数不在数组中，则输出“无此数”。-15 by descending number of sequentially placed in an array, enter a few, asked to use binary search method to find the first number is the array of several elements of value. If