通过递归实现二分法，以递归的方式能快捷直接的实现平时要比较麻烦的二分法查询功能-//　　Function: FindStringInSortedArray

//　　Usage: index = FindStringInSortedArray (key, array, n)

//　　-------------------------------------------------------------

//　　The function searchs the array looking for the specified key.

//　　The argument n specifies the effective size of the array, which must

//　　be sorted according to the lexicographic order imposed by StringCompare.

//　　If the key is found, the order imposed by StringCompare. If the key is found, the order imposed by

//　　StringCompare. If the key is found, the function returns the index in the array at which that key appears.

//　　(If the key appears more than once in the array, any of the mathcing indices may be returned). If the key

//　　does not exist in the array, the funcion returns-1. In this implementation, FindStringInSortedArray is simply

//　　a wrapper　all the work is done by the recursive function BinarySearch.