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Lecture 8

OOP with C# by Dr.hakim

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Lecture 8

  1. 1. Ar rays(I) Lecture 8 Dr. Hakem Beitollahi Computer Engineering Department Soran University
  2. 2. Outline  Arrays  Declaring and allocating arrays  Examples using arrays Arrays(I)— 2
  3. 3. Arrays Arrays(I)— 3
  4. 4. Arrays (I)  An array is a group of contiguous memory locations that all have the same name and type  To refer to a particular location or element in the array, we specify the name of the array and the position number  Array indexes  Position number used to refer to a specific location/element  Also called subscript  Place in square brackets o Must be positive integer or integer expression  First element has index zero  Example (assume a = 5 and b = 6) o c[ a + b ] = c[11] = 2; Arrays(I)— 4
  5. 5. Arrays (II) Arrays(I)— 5
  6. 6. Arrays (III) A -- -- -- -- -- -- -- -- -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9] Arrays(I)— 6  Suppose int[] A = new int [10]; // array of 10 uninitialized ints  To access an individual element we must apply a subscript to list name A
  7. 7. Arrays (IV) Arrays(I)— 7  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A -- -- -- -- -- -- -- -- -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  8. 8. Arrays (V) Arrays(I)— 8  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- -- -- -- -- -- -- -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  9. 9. Arrays (VI) Arrays(I)— 9  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- -- -- -- -- -- 5 -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  10. 10. Arrays (VII) Arrays(I)— 10  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- 8 -- -- -- -- 5 -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  11. 11. Arrays (VIII) Arrays(I)— 11  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- 8 6 -- -- -- 5 -- -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  12. 12. Arrays (IX) Arrays(I)— 12  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- 8 6 -- -- -- 5 12 -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  13. 13. Arrays (X) Arrays(I)— 13  Consider int i = 7, j = 2, k = 4; A[0] = 1; A[i] = 5; A[j] = A[i] + 3; A[j+1] = A[i] + A[0]; A[A[j]] = 12; A 1 -- 8 6 3 -- -- 5 12 -- A[0] A[1] A[2] A[3] A[4] A[5] A[6] A[7] A[8] A[9]
  14. 14. Common Programming Error 7.1  It is important to note the difference between the “seventh element of the array” and “array element seven.” Array subscripts begin at 0, thus the “seventh element of the array” has a subscript of 6, while “array element seven” has a subscript of 7 and is actually the eighth element of the array. Arrays(I)— 14
  15. 15. Array Definition (I) Arrays(I)— 15
  16. 16. Array Definition (II)  When arrays are allocated, the elements are initialized to zero for the numeric primitive data-type variables, to false for bool variables and to null for reference types.  Multiple declaration in single line:  In an array of value types, every element of the array contains one value of the declared type.  For example, every element of an int array is an int value. Arrays(I)— 16 string[] b = new string[ 100 ], x = new string[ 27 ]; double[] array1 = new double[ 10 ], array2 = new double[ 20 ];
  17. 17. Examples Using Arrays Arrays(I)— 17
  18. 18. Initializing the elements of an array  Example 1: Allocating an Array and Initializing Its Elements  The program creates three integer arrays of 10 elements and displays those arrays in tabular format. The program demonstrates several techniques for declaring and initializing arrays Arrays(I)— 18
  19. 19. Arrays(I)— 19
  20. 20. Summing the elements of an array  Example 2: Totaling the Elements of an Array  Often, the elements of an array represent series of values to be used in calculations.  Elements of an array represent the grades for an exam, the professor may wish to total the elements, then calculate the class average. Arrays(I)— 20
  21. 21. Arrays(I)— 21
  22. 22. Histogram Example  Example 3: Using Histograms to Display Array Data Graphically  Many programs present data to users in a graphical manner  Numeric values often are displayed as bars in a bar chart.  In such a chart, longer bars represent larger numeric values.  One simple way to display numeric data graphically is with a histogram that shows each numeric value as a bar of asterisks (*). Arrays(I)— 22
  23. 23. Arrays(I)— 23 Show length of an array
  24. 24. Use arrays as counters  Example 4: Using the Elements of an Array as Counters  Sometimes programs use a series of counter variables to summarize data, such as the results of a survey.  Calculate the number of occurrences of each side on a six-sided die Arrays(I)— 24
  25. 25. Arrays(I)— 25

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