1 / 13

Two-Dimensional Data

Two-Dimensional Data. Class of 5 students Each student has 3 test scores Store this information in a two-dimensional array First dimension: which student 0, 1, 2, 3 or 4 Second dimension: which test score 0, 1, or 2. Declaring a 2D Array.

benny
Télécharger la présentation

Two-Dimensional Data

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Two-Dimensional Data • Class of 5 students • Each student has 3 test scores • Store this information in a two-dimensional array • First dimension: which student 0, 1, 2, 3 or 4 • Second dimension: which test score 0, 1, or 2

  2. Declaring a 2D Array • Give a second pair of square brackets to tell C++ you want a 2D array • Example: int grades[5][3];

  3. Creating a 2D Array • Create array elements by telling how many ROWS and COLUMNS • Example: int grades[5][3]; grades is a two-dimensional array, with 5 rows and 3 columns. One row for each student. One column for each test. C++ arrays are row major, which means that we always refer to the row first.

  4. Initializing Elements // First student scores grades[0][0] = 78; grades[0][1] = 83; grades[0][2] = 82; Write assignment statements to fill-in the rest of the array.

  5. Declare & Create & Initialize Short Cut • Example: int grades[5][3] = { { 78, 83, 82 }, { 90, 88, 94 }, { 71, 73, 78 }, { 97, 96, 95 }, { 89, 93, 90 } }; A Two-D Array is an array of arrays. Each row is itself a One-D array.

  6. Row, Column Indices 0 1 2 0 1 2 3 4 Give both the ROW and COLUMN indices to pick out an individual element. The fourth student’s third test score is at ROW 3, COLUMN 2

  7. What are the elements of the array table? int table[3][4]; x = 1; for (row = 0; row < 3; row++) for (col = 0; col < 4; col++) { table[row][col] = x; x++; } //for col column row

  8. Exercise: Average Overall • Find the average test score of all students’ test scores. • Use rows to tell you how many rows in the 2D array. • Use cols to tell you how many columns in the 2D array.

  9. Exercise: Average Overall int sum = 0; for(int r = 0; r < rows; r++) for(int c = 0; c < cols; c++) sum = sum + grades[r][c]; int avg = sum / (rows*cols);

  10. Write a function that prints out the elements in a 2-D array (as they appear in the matrix)

  11. Exercise: print 2-D array void printArray(int matrix[][]) { for(inti = 0; i < matrix.length; i++) { for(int j = 0; j < matrix[0].length; j++) cout << (matrix[i][j] << ” “); cout << endl; } }

  12. Write a function that returns the maximum element in a 2-D array. • Things work pretty much the same way with 3-D arrays (and 4-D and …)

  13. Exercise: find maximumin a 2D array intfindMax(int matrix[][COLS], int r, int c) { int max = matrix[0][0]; for(inti = 0; i < r; i++) for(int j = 0; j < c; j++) if ( matrix[i][j] > max) max = matrix[i][j]; return max; }

More Related