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Chapter 7

Chapter 7. Multidimensional Arrays. Defining a two dimensional array. elementType [][] arrayName ; // Java pro elementType arrayName [][]; // C++ alternate For example: int [][] chessboard; To allocate space for the array, use new : chessboard = new int [8][8];

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Chapter 7

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  1. Chapter 7 Multidimensional Arrays

  2. Defining a two dimensional array • elementType[][] arrayName; // Java pro • elementTypearrayName[][]; // C++ alternate • For example: int[][] chessboard; • To allocate space for the array, use new: chessboard = new int[8][8]; • Or int[][] chessboard = new int[8][8];

  3. Accessing elements • int king = 10; • chessboard[0][4] = king; • int piece = chessboard[7][3]; • Each dimension must use a pair of brackets around the index [] • Do not try chessboard[7, 3] notation

  4. Initializing multiple dimensions

  5. What’s an array? • A two-dimensional array is actually a one-dimensional array where each element is a one-dimensiona array • An “array of arrays” is an important concept! • Each array has its own length property • Array lengths can be different (ragged array)

  6. The lengthproperty in action

  7. Rectangular versus ragged arrays • A rectangular array has the same number of elements in each array for a given dimension • int[][] myArray = new int[5][7]; • myArray has 5 x 7 = 35 elements, with 7 elements in each of the 5 rows • A ragged array has varying numbers of elements in a given dimension, as illustrated on the next slide:

  8. Ragged array definition

  9. The contents of a ragged array

  10. Another array initialization example

  11. Passing a two-dimensional array as an argument to a method

  12. Multiple Dimensional Arrays • An array of arrays of arrays of…. • Each dimension can consist of rectangular or ragged arrays • Each dimension is enclosed with a pair of brackets • Maximum number of dimensions is nominally 255 for the VM*

  13. Three-dimensional ragged array

  14. Lab 2 • Write a program to create a chessboard stored as a two-dimensional character array • Chess is played on an 8 x 8 square board with a total of 64 squares • Empty squares can be represented by a space • Abbreviate pieces as ‘R’ = rook, ‘N’ = knight, ‘B’ = Bishop, ‘Q’ = queen, ‘K’ = king, ‘P’ = pawn • Initialize the array according to the diagram

  15. What the array dimensions mean • The columns will be the first array dimension • Label columns ‘a’ – ‘h’ • Column a is the 0 index, h is the 7 index • The rows will be the second array dimension • Number rows 1-8 • Row 1 is the 0 index, 8 is the 7 index

  16. What to do and turn in • Write a method that creates a two-dimensional character array, initializes it with the starting chessboard as shown in the diagram, and returns the array • Write a method that prints the chess board contents and the row/column labels • Turn in a screen shot of the chess board • Turn in a print-out of your program

  17. What the chessboard looks like:

  18. Extra Credit (10%) • Write a user interface that makes a move • The notation is the letter/number of the start location and the letter/number of the end location (e.g. “d1 g4” would move the white queen diagonally 3 squares) • Allow any move (don’t check legality) • Print an updated view of the board showing the pieces after the move

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