Computer Science Canada Binary Search Help! |
| Author: | Fallis15 [ Mon Jan 14, 2008 6:43 pm ] |
| Post subject: | Binary Search Help! |
I have to do this for school and i need to replace the "search" procedure so that its linear search and not binary search, but even before i can do that i have a problem. its this example i copied down from the workbook, but it doesn't give you the example of the text file to be opened and searched in so i dont know how to set up the text file so it reads properly, i make the name, adress and phone for each student justified so that it has the 30, 30, and 8 characters for each but it still doesnt find the student when i run the program and type in one of the names, any suggestions? This is the program starting here =================================================== % The "BinarySearch" program % Finds a particular record in a sorted file % Using the binary search method type studentType : record name : string (30) address : string (30) phone : string (8) end record const maxFile := 500 var studentFile : array 1 .. maxFile of studentType var count : int procedure readFile % Uses global variables var students : int open : students , "studentFile.txt", get assert students > 0 count := 0 loop get : students, skip exit when eof (students) count := count + 1 get : students, studentFile (count).name : 30, studentFile (count).address : 30, studentFile (count).phone : 8 end loop put "There are ", count, " students in file" end readFile procedure search (studentFile : array 1 .. * of studentType, var key : string (*), count : int, var place : int) var first, last, middle : int if length (key) <= 30 then % Pad with blanks key := key + repeat (" ", 30 - length (key)) end if % Initialize the binary search first := 1 last := count % Search until one element is left % If key sought is in list this will be it loop middle := (first + last) div 2 if studentFile (middle).name >= key then % Discard last half of list last := middle else % Discard first half of list including middle first := middle + 1 end if % exit when only one record left exit when first >= last end loop if studentFile (first).name = key then place := first else place := 0 end if end search readFile var nameSought : string (30) loop var place : int put "Enter name of student to be found (\"stop\" to exit)" get nameSought : * exit when nameSought = "stop" search (studentFile, nameSought, count, place) if place not= 0 then bind sought to studentFile (place) put "name" : 30, "address" : 30, "phone" : 8 put sought.name : 30, sought.address : 30, sought.phone : 8 else put "Not In File!!" end if end loop ====================================================== |
|