An Introduction to Programming with C++ Sixth Edition

1. An Introduction to Programming with C++Sixth Edition Chapter 12 Two-Dimensional Arrays

2. Objectives • Declare and initialize a two-dimensional array • Enter data into a two-dimensional array • Display the contents of a two-dimensional array • Sum the values in a two-dimensional array • Search a two-dimensional array • Pass a two-dimensional array to a function An Introduction to Programming with C++, Sixth Edition

3. Using Two-Dimensional Arrays • Recall that an array is a group of related variables that have the same data type • You can visualize a one-dimensional array as a column of variables in memory • You can visualize a two-dimensional array as a table in that the variables are in rows and columns • You can determine the number of variables in a two-dimensional array by multiplying the number of rows by the number of columns An Introduction to Programming with C++, Sixth Edition

4. Using Two-Dimensional Arrays (cont’d.) • Each variable in a two-dimensional array is identified by a unique combination of two subscripts specifying the variable’s row and column position • Variables located in the first, second, etc. row of a two-dimensional array are assigned a row subscript of 0, 1, etc. • Similarly, variables located in the first, second, etc. column of a two-dimensional array are assigned a column subscript of 0, 1, etc.  An Introduction to Programming with C++, Sixth Edition

5. Using Two-Dimensional Arrays (cont’d.) • You refer to each variable in a two-dimensional array by the array’s name immediately followed by the variable’s row and column subscripts (in that order), each enclosed in its own set of square brackets • As with one-dimensional arrays, the last row and column subscripts of a two-dimensional array will always be one less than the number of rows and columns (respectively) in the array, since the subscripts begin at 0 An Introduction to Programming with C++, Sixth Edition

6. Figure 12-1 Names of some of the variables in the two-dimensional orders array An Introduction to Programming with C++, Sixth Edition

7. Using Two-Dimensional Arrays (cont’d.) Figure 12-2 Problem specification for the Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

8. Figure 12-2 IPO chart for the Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

9. Declaring and Initializing a Two-Dimensional Array • You must declare a two-dimensional array before you use it • As with one-dimensional arrays, it is good practice to initialize the array variables • Syntax for declaring a two-dimensional array: dataType arrayName [numberOfRows] [numberOfColumns] = {{initialValues}, {initialValues }, …{initialValues }}; • dataType specifies the data type of elements in the array (all elements must have same data type) • numberOfRows and numberOfColumns specify number of rows and columns in array, respectively An Introduction to Programming with C++, Sixth Edition

10. Declaring and Initializing a Two-Dimensional Array (cont’d.) • You initialize elements in a two-dimensional array by entering a separate initialValues section, enclosed in braces, for each row of the array • Maximum number of initialValues sections you may enter is the number of rows in the array • Within individual initialValues sections, you enter one or more values separated by commas • Maximum number of values you may enter in a row is the number of columns An Introduction to Programming with C++, Sixth Edition

11. Figure 12-3 How to declare and initialize a two-dimensional array An Introduction to Programming with C++, Sixth Edition

12. Declaring and Initializing a Two-Dimensional Array (cont’d.) Figure 12-4 Illustration of the two-dimensional grades array An Introduction to Programming with C++, Sixth Edition

13. Entering Data into a Two-Dimensional Array • You can use either an assignment statement or the extraction operator to enter data into the elements of a two-dimensional array • Syntax for assignment statement: arrayName [rowSubscript] [columnSubscript ] = expression; • expression can include any combination of constants, variables, and operators • Must match data type of array An Introduction to Programming with C++, Sixth Edition

14. Entering Data into a Two-Dimensional Array (cont’d.) • Syntax for extraction operator: cin >> arrayName [rowSubscript][columnSubscript ]; An Introduction to Programming with C++, Sixth Edition

15. Figure 12-5 How to use an assignment statement to assign data to a two-dimensional array An Introduction to Programming with C++, Sixth Edition

16. Figure 12-5 How to use an assignment statement to assign data to a two-dimensional array (cont’d.) An Introduction to Programming with C++, Sixth Edition

17. Figure 12-6 How to use the extraction operator to store data in a two-dimensional array An Introduction to Programming with C++, Sixth Edition

18. Figure 12-6 How to use the extraction operator to store data in a two-dimensional array (cont’d.) An Introduction to Programming with C++, Sixth Edition

19. Displaying the Contents of a Two-Dimensional Array • To display the contents of a two-dimensional array, you must access its individual elements • You can use two counter-controlled loops • One to keep track of the row subscript • One to keep track of the column subscript An Introduction to Programming with C++, Sixth Edition

20. Figure 12-7 How to display the contents of a two-dimensional array An Introduction to Programming with C++, Sixth Edition

21. Figure 12-7 How to display the contents of a two-dimensional array (cont’d.) An Introduction to Programming with C++, Sixth Edition

22. Coding the Caldwell Company’s Orders Program • Program that uses a two-dimensional array to store the number of orders received from each of the Caldwell Company’s four sales regions during the first three months of the year • Each row in the array represents a region, and each column represents a month • Program allows the user to enter the order amounts and then displays the amounts on the computer screen An Introduction to Programming with C++, Sixth Edition

23. Coding the Caldwell Company’s Orders Program Figure 12-8 IPO chart information and C++ instructions for the Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

24. Figure 12-8 IPO chart information and C++ instructions for the Caldwell Company’s orders program (cont’d.) An Introduction to Programming with C++, Sixth Edition

25. Figure 12-9 The Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

26. Figure 12-10 Sample run of the Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

27. Accumulating the Values Stored in a Two-Dimensional Array • Program for the Jenko Booksellers company uses a two-dimensional array to store the sales made in each of the company’s three bookstores • Array contains three rows and two columns • First column contains sales amount for paperback books sold in each of three stores • Second column contains sales amounts for hardcover books in the three stores • Program calculates total sales by accumulating amounts stored in array and displays total sales An Introduction to Programming with C++, Sixth Edition

28. Figure 12-11 Problem specification, IPO chart information, and C++ instructions for the Jenko Booksellers program An Introduction to Programming with C++, Sixth Edition

29. Accumulating the Value Stored in a Two-Dimensional Array (cont’d.) Figure 12-11 Problem specification, IPO chart information, and C++ instructions for the Jenko Booksellers program (cont’d.) An Introduction to Programming with C++, Sixth Edition

30. Figure 12-12 The Jenko Booksellers program An Introduction to Programming with C++, Sixth Edition

31. Accumulating the Value Stored in a Two-Dimensional Array (cont’d.) Figure 12-13 Result of running the Jenko Booksellers program An Introduction to Programming with C++, Sixth Edition

32. Searching a Two-Dimensional Array • Program for the Wilson Company uses a four-row, two-column array to store the company’s four pay codes and their corresponding pay rates • Pay codes are stored in first column of each row • Pay rate associated with each code is stored in the same row as its pay code, in the second column • Program gets a pay code from user and searches for pay code in the array’s first column • If pay code is found, corresponding pay rate is displayed; otherwise, “Invalid pay code” is displayed An Introduction to Programming with C++, Sixth Edition

33. Figure 12-14 Problem specification, IPO chart information, and C++ instructions for the Wilson Company program An Introduction to Programming with C++, Sixth Edition

34. Figure 12-14 Problem specification, IPO chart information, and C++ instructions for the Wilson Company program (cont’d.) An Introduction to Programming with C++, Sixth Edition

35. Figure 12-14 Problem specification, IPO chart information, and C++ instructions for the Wilson Company program (cont’d.) An Introduction to Programming with C++, Sixth Edition

36. Figure 12-15 Sample run of the Wilson Company program Figure 12-16 Another sample run of the Wilson Company program An Introduction to Programming with C++, Sixth Edition

37. Figure 12-17 Wilson Company program An Introduction to Programming with C++, Sixth Edition

38. Figure 12-17 Wilson Company program (cont’d.) An Introduction to Programming with C++, Sixth Edition

39. Searching a Two-Dimensional Array (cont’d.) Figure 12-18 Desk-check table after the statements on lines 11 through 21 are processed An Introduction to Programming with C++, Sixth Edition

40. Searching a Two-Dimensional Array (cont’d.) Figure 12-19 Desk-check table after the nested loop is processed the first time An Introduction to Programming with C++, Sixth Edition

41. Searching a Two-Dimensional Array (cont’d.) Figure 12-20 Desk-check table after the nested loop is processed the second time An Introduction to Programming with C++, Sixth Edition

42. Searching a Two-Dimensional Array (cont’d.) Figure 12-21 Desk-check table after the nested loop ends during the second search An Introduction to Programming with C++, Sixth Edition

43. Passing a Two-Dimensional Array to a Function • Like one-dimensional arrays, two-dimensional arrays are passed automatically by reference • When passing a two-dimensional array to a function, function header and prototype should contain formal parameter consisting of name of array followed by two sets of square brackets containing the number of rows and columns, respectively • Number of rows is not required (first set of brackets may be left empty) An Introduction to Programming with C++, Sixth Edition

44. Figure 12-22 Modified Caldwell Company’s orders program An Introduction to Programming with C++, Sixth Edition

45. Figure 12-22 Modified Caldwell Company’s orders program (cont’d.) An Introduction to Programming with C++, Sixth Edition

46. Summary • A two-dimensional array resembles a table in that elements are in rows and columns • Each element has the same data type • You can determine the number of elements in a two-dimensional array by multiplying the number of rows by the number of columns • Each element in a two-dimensional array is identified by a unique combination of two subscripts representing the element’s row and column, respectively An Introduction to Programming with C++, Sixth Edition

47. Summary (cont’d.) • You refer to each element in a two-dimensional array by the array’s name immediately followed by the element’s subscripts in two sets of square brackets • First row and column subscripts in a two-dimensional array are 0 • Last row and column subscripts are always one number less than the number of rows and columns, respectively • You must declare a two-dimensional array before you can use it An Introduction to Programming with C++, Sixth Edition

48. Summary (cont’d.) • When declaring a two-dimensional array, you must provide the number of rows as well as the number of columns • You can use an assignment statement or the extraction operator to enter data into an array • You need to use two loops to access every element in a two-dimensional array • One of the loops keeps track of the row subscript, and the other keeps track of the column subscript An Introduction to Programming with C++, Sixth Edition

49. Summary (cont’d.) • To pass a two-dimensional array to a function, you include the array’s name in the statement that calls the function • Array’s corresponding formal parameter in the function header must specify the formal parameter’s data type and name, followed by two sets of square brackets • First bracket contains the number of rows, and the second bracket contains the number of columns An Introduction to Programming with C++, Sixth Edition

50. Lab 12-1: Stop and Analyze • Study the program in Figure 12-23 and then answer the questions • The company array contains the amounts the company sold both domestically and internationally during the months January through June • The first row contains the domestic sales for the three months • The second row contains the international sales during the same period An Introduction to Programming with C++, Sixth Edition