Overview. Arrays and their properties Creating arrays Accessing array elements Modifying array elements Loops and arrays. Initialization Searching

Transcription

1 Arrays

2 Overview Arrays and their properties Creating arrays Accessing array elements Modifying array elements Loops and arrays Initialization Searching

3 Arrays and Their Properties Hold several values of the same type (homogeneous) Based on a slot number (the index number) Instant access Linear (one after the other) Static once their size is set, it s set

4 What arrays look like Things to notice myarray 5 6 There are 7 slots, with index numbers 0 6 The name of the array is myarray Easy to be off by one

5 Creating Arrays <data type>[] <name> = new <data type> [<size>]; new brings complex variables to life in C# Notice that we can create an array of any data type, just by changing the data type!

6 Examples An array of shorts: short[] somearray = new short[50]; An array of floats: float[] myarray = new float[25]; An array of booleans: bool[] list = new bool[65]; An array of chars: char[] characters = new char[255];

7 Initializing Arrays with Values <data type>[] <name> = new <data type> [<size>] {VALUES}; Or <data type>[] <name> = {VALUES};

8 Modifying an Array You must specify which slot you are putting information in Example: int[] myarray = new int[50]; myarray[3] = 12; 49 This won t work: int[] myarray = new int[50]; myarray = 12; Data type on the left of = is an array Data type on right of = is an int 12

9 Accessing Information Copying information out of a particular slot Example: int clientage; clientage = myarray[4]; This copies information from the fifth slot (slot four) into the variable clientage

10 Initializing Arrays (large arrays) For most arrays, you will use a loop to initialize Problem: create an array of 50 bytes and fill each slot with the number 42 Solution: byte[] mylist = new byte[50]; for (int =0; < 50; ++) { } mylist[] = 42;

11 Line by Line (a smaller example) byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

12 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

13 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

14 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

15 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

16 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

17 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

18 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

19 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

20 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

21 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

22 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

23 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

24 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

25 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

26 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

27 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

28 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

29 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

30 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

31 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

32 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

33 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; }

34 Line by Line byte[ ] mylist = new byte[5]; for (int = 0; < 5; ++) { mylist [] = 42; } false

35 Finding the Smallest Element If you were given an array of numbers, how would YOU do it? Computers can only compare two at a time Go through entire list Keep track of smallest so far Let s assume We have an array of 5 integers The array contains random unknown numbers The name of the array is called randomarray

36 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

37 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

38 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

39 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

40 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

41 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar Is 42 > 17?

42 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for 1 smallestsofar

43 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

44 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for 2 smallestsofar

45 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

46 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; 2 Is 17 > 42? smallestsofar

47 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

48 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for 3 smallestsofar

49 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

50 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar Is 17 > -8?

51 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

52 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

53 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for 4 smallestsofar

54 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for 4 smallestsofar

55 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar Is -8 > 4?

56 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

57 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

58 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { }//if }//for smallestsofar = randomarray[]; smallestsofar

59 Another Trace int smallestsofar; smallestsofar = randomarray[0]; for (int = 1; < 5; ++) { if (smallestsofar > randomarray[]) { smallestsofar = randomarray[]; }//if }//for smallestsofar

60 Summary Arrays hold values that are all the same type Arrays are static in size Creating arrays always follows a format You can create an array of any type To initialize or search arrays, you ll almost always use a loop