Chapter 10 –Multi-Dimensional Numeric Arrays

1. Chapter 10 –Multi-Dimensional Numeric Arrays

2. Name of array Two sets of [ ] so two dimensional Type of array Multidimensional Arrays • Visual image of matrix or table for two-dimensional array • Subscript for each dimension • Declared with value for each dimensionint b[2] [3]; Number of elements 2*3 = 6 Lesson 10.1

3. Initializing • Initialized by row • Example: int b[2] [3] ={51, 52, 53, 54, 55, 56}; • Elements would be:b[0] [0] = 51 b[0] [1] = 52 b[0] [2] = 53b[1] [0] = 54 b[1] [1] = 55 b[1] [2] = 56 Remember – subscripts begin at zero! Lesson 10.1

4. Initializing • Can use braces to separate rows int c [4] [3] = {{ 1, 2, 3}, { 4, 5, 6}, { 7, 8, 9}, {10, 11, 12}}; Advantage is visual table! Lesson 10.1

5. int c[ ] [3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}, {10,11,12}}; If far left dimensionsize left blank, it isdeclared implicitlyby values given – inthis case 4 rows. Initializing int c[4] [3] = {{1,2}, {4, 5, 6}, {7}, {10,11,12}}; If values left outof row, implicitly initialized to zero. c[2] [2] = 0 Lesson 10.1

6. Creates new line or row Printing for (j = 0; j < 2; j++) { for (k = 0; k < 3; k++) { cout << b[j] [k]; } cout << endl; } • Usually use nested for loop • Two dimensions, two loops • First loop controls rows • Second loop controls columns Lesson 10.1

7. Read number of columns and rows from file prior to array elements Reading Array From File infile >> num_rows >> num_cols; for (j = 0; j < num_rows; j++) { for (k = 0; k < num_cols; k++) { infile >> a[j] [k]; } } Lesson 10.2

8. Storage of Two-Dimensional Arrays • Fills row by row • If have fewer elements, then storage to the right of those filled un-initialized elements • Three and greater dimensions • Far right subscript increments first • Other subscripts increment in order from right to left Lesson 10.2

9. Storage If file gave number of rows as 3 and number of columns as 4 then have non-contiguous storage. array[5] [9] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 1 2 3 4 * * * * * 2 4 6 8 * * * * * 3 5 7 9 * * * * * * * * * * * * * * * * * * * * * * * Lesson 10.2

10. array size e[I] [J] [K] array element, e[x] [y] [z] array size e[2] [3] [4] array element, e[0] [1] [2] Storage Location • Formula to locate arrays element's position in memory sequence location = x * (J * K) + y * (K) + z +1 sequence location = 0 * (3 *4) + 1 * (4) + 2+1 = 7 Lesson 10.2

11. Passing Array to Function Declaration void funcName (type, type, type[ ] [max_cols]); Call funcName (rows, cols, arrayName); void funcName (type r, type c, type array[ ] [max_cols]); Header Lesson 10.2

12. const Qualifier • Place in front of array name in function declaration and header • Assures that array is not modified in function void funcName (type, type, const type [ ] [ col ]); Declaration Lesson 10.2

13. Summary Learned how to: • Initialize multidimensional arrays • Print multidimensional arrays • Read a file for array element values • Visualize storage • Pass an array to a function