Programming in OOP/C++

Transcription

1 Introduction Lecture 3-2 Programming in OOP/C++ Arrays Part (2) By Assistant Professor Dr. Ali Kattan 1

2 Arrays Examples Solutions for previous assignments Write a program to enter and store your name and 4 marks. Then print your name with the average. You can only enter a single string and no spaces allowed When we use strings without initialization, we must declare a size. The size we choose should be suitable for our application (more, not less) 2

3 Arrays Examples Solutions for previous assignments Write a program to enter City name, Area Name and print the sentence: I live in area xxxxxx of yyyyyy city. When we use strings without initialization, we must declare a size. The size we choose should be suitable for our application (more, not less) 3

4 Arrays Examples Solutions for previous assignments Write a program to declare 2 double arrays of size N and store the multiplication result of element in a third array then print it. 4

5 Arrays of Strings Suppose that we want to make a list of items and their prices: Bread $1.5 Eggs $3.8 Meat $15.2 Milk $2.5 We want to represent the item name with its price inside a program? 5

6 Arrays of Strings In this case we will need two arrays, one to store the item s name and the other to store the price. The program below is an example to enter such lists. Pay attention to char item [size][12]; 6

7 Arrays of Strings char item [4][12]; There 4 strings each is a maximum of 12 characters Bread Eggs Meat Milk 7

8 Sorting Sorting means arranging the elements of an array in either descending order (from high to low), or ascending order (from low to high) Unsorted Sorted (ascending) Sorted (descending) 8

9 Sorting There are several sorting algorithms such as: Selection Sort. Bubble Sort. Counting Sort Insertion Sort. Quick Sort. Merge Sort. Heap Sort. We will study the first two only. Selection sort is explained in this lecture and bubble sort & counting sort is left as a homework. 9

10 Sorting: Selection Sort Swapping 10

11 Sorting: Selection Sort Understanding Swapping Before we explain Selection Sort, we explain what is swapping. Swapping is exchanging the values between 2 variables. For example if A=30 and B=50, swapping means that we want to exchange the values of A and B such that A takes the value of B and B takes the value of A. A = 30, B = 50; A = B; B = A; WRONG!! To do this we will need a 3rd variable, let s call it temp. 1. A is 30 and B is Store current A value in Temp. 3. A takes the current value of B. 4. B takes A s original value from temp temp = A; A = B; B = temp; 11

12 Sorting: Selection Sort Understanding The Algorithm Selection sort is a combination of searching and sorting. It uses arrays and nested loops to do the job. Outer loop starts from the first element of the array to the one before the last. Inner loop starts from current outer loop value+1 to last element of the array. See Video 12

13 Sorting: Selection Sort Understanding The Algorithm Steps for sorting array of 6 numbers. Outer loop is i, inner loop is j j i 13

14 Assignment 1. Write a program to enter 5 students names such that you use one array to enter first name and another array to enter last name. Print all the names after entry. 2. Write a program to enter 6 shopping list items that contains item name (string), item quantity (integer) and item price (float). Then find the total of the list (each item quantity x price then sum all). 3. Write a program to enter 10 integers then sort them in a descending way (from high to low). 14

15 Remember: If you don t practice C++ programming on the computer, YOU WILL NOT LEARN ANYTHING. To become a professional programmer you must try all the examples by yourself on a computer. 15

16 How can I get the lecture notes? Check the website One hardcopy will be provided after the lecture for photocopying. By ali.kattan@nobleinst.krd (if there is a problem only) 16