scis.regis.edu ● CS-362: Data Structures Week 4 Dr. Jesús Borrego Lead Faculty, COS Regis University 1

Topics String functions Records Mid Term 2

String Functions Size of string: aString.size() Find substring in string: aString.find ( substr ) Create substring: newStr = aString.substr (fm, to) Program String Functions 3

Records The course is about data structures – the structure of data We saw files and arrays Now, we cover a new type of data structure: records 4

Records If we have a student database with a Students table, each student will be a record Records in C++ are called structures (struct) Records allow elements (fields) of different types to be defined. For a Student record: 5 Field nameType LnameText FnameText AgeInt ClassEnumerated (Fr, Sp, Jr, Sr) DOBdate

Struct struct nameOfStructure { datatype1 variable1; datatype2 variable2; … datatypen variablen; } 6

Defining a Student record struct Students { string lname; string fname; char mi; double gpa; }; 7

Program Beatles struct student { float mid_term; float final; char grade; }; struct student john; struct student paul; struct student ringo; struct student george; 8

Program Beatles – (Cont’d) struct student { float mid_term; float final; char grade; } john, paul, ringo, george; 9

Accessing record fields To access a field in a record, use the record variable name followed by a dot (“.”) and then the field name: john.grade = ‘A’; Note that we use the variable, not the record name 10

Record definition Struct defines a data type but does not declare a variable No memory is allocated when we describe struct When we define variables of struct, then memory is allocated We can input values directly into the field name cin>> john.grade; 11

Record assignment We can assign values to a field in a record john.grade = ‘A’; If we try to read a record from the keyboard, we will find that cin is not defined for the record cin >> john; Need to enter each field individually ▫Or create a new cin that reads all elements of a record 12

Comparing fields in a record We can compare fields in one record to those in another: if ( john.grade == paul.grade ) See Beatles program 13

Initializing a record struct student { float mid_term; float final; char grade; }; struct student john = { 75.4, 80.6, ‘B’ }; 14

Arrays and Records Both arrays and records define multiple elements using a single name Arrays have elements of the same type Records have fields that may be of different types Arrays are passed by reference to functions Records can be passed by reference OR by value Arrays cannot be returned from a function Records can be returned from a function 15

Arrays and Records (Cont’d) We can have arrays of records struct student { float mid_term; float final; char grade; }; student Students [ MAX ]; Students [ i ].grade = ‘A’ 16

Arrays and Records (Cont’d) We can have records of arrays struct student { float mid_term; float final; char grade; string courses [ NUM ]; }; student aStudent; aStudent.courses [ i ] = “CS 362”; 17

Records in Records struct nameType { string first; string last; char mi; }; struct Employee { nameType name; string empID; double salary; } 18

Records in Records (Cont’d) struct nameType { string first; string last; char mi; }; struct Employee { nameType name; string empID; double salary; } 19 Employee Joe; Joe.name.first = ”Joe”; Joe.name.last = “Vega”; Joe.name.mi = ‘F’; Joe.empid = “123ABC”; Joe.salary = 60000;

Program Structs Defines a month record Contains number of days Contains array of characters for name of month Creates an array of records See structs.cpp See structs1.cpp 20

Records as parameters As with other types, we can pass records to functions See RecStruct 21

Example of passing records to functions See Tomorrow.cpp See Time.cpp 22

Mid term Will cover file processing, enumerated types, single dimension arrays, sorts (bubble, insertion, selection), sequential search, binary search. About 7 questions and 1 program. Due before week 6 Submit to Week 4 assignments 23

Questions to 24