Arrays and Strings

1. Arrays and Strings CSCI293 - C# September 26, 2005

2. Refresher: declaring arrays int[] myarray = new int [10]; Step One - declare myarray to be a variable holding a list of integers Step Two - allocate space for myarray

3. The foreach Statement float[] bob = {1.1f, 2.2f, 3.3f, 4.4f, for (int i=0; i < bob.Length; i++) Console.WriteLine ("{0}", bob[i]); foreach (float x in bob) Console.WriteLine ("{0}", x);

4. Multi-Dimensional Arrays • Each dimension of a multi-dimension array can be the same (like in C++) • for example, 5 rows each of length 10 int[][] myArray = new int[5][10]; • Each dimension can be a different size • first row's length is 10, but second row's length is 15 int[][] myWeirdArray = new int[2][]; myWeirdArray[0] = new int[10]; myWeirdArray[1] = new int[15];

5. Passing Arrays as Parameters public int largest (params int[] thelist) { int max = thelist[0]; foreach (int value in thelist) if (value > max) max = value; return max; } Then inside main(): Class1 tempvar = new Class1(); int largest; int[] myarray = {8,2,3,9,4}; largest = tempvar.largest (myarray); Console.WriteLine ("largest = {0}", largest); largest = tempvar.largest (10, 40, 20, 30); Console.WriteLine ("largest = {0}", largest);

6. Sorting and Searching Array.Sort (myarray); Console.Write ("sorted array = "); foreach (float value in myarray) Console.Write("{0} ",value); Console.WriteLine(); int index = Array.BinarySearch(myarray,4); Console.WriteLine("4 is at array index {0}", index);

7. Other Array Functions // you don't need a for loop to copy an array Array.Copy(oldarray,0,newarray,0,oldarray.Length); // reverse an array Array.Reverse (myarray); //how long is the array? for (int i=0; i<myarray.Length; i++) // where is the value 99 in my list? location = Array.IndexOf (myarray, 99);

8. Creating Strings string name1 = "Steve Dannelly"; string name2 = "BOB";

9. Comparing Strings Unlike C++, where you must use strcmp to compare the contents of two strings, in C# you can use == if (name2 == name2.ToUpper()) Console.WriteLine("all uppercase"); else Console.WriteLine("not uppercase"); But, you still can not use < or > if (string.Compare(name1,name2) < 0) Console.Write("name1 < name2");

10. Other String Functions • Length • Copy • PadLeft • PadRight • + • Note that "string" ≠ "char[]". So the list of string methods is different from the list of array methods • for example, there is no string.reverse • but you can do this: mystring[0] = 'A';