Downloaded 19 times
Uploaded byMustafa Qureshi
Algorithm and psuedocode
The document discusses algorithms and pseudocode, explaining the phases of programming: problem solving and implementation. It emphasizes the role of pseudocode in designing algorithms using an informal language similar to English, and provides various examples of algorithms for tasks such as calculating interest, checking odd/even numbers, and identifying prime numbers. The text also includes practical programming tasks, such as reversing integers and strings, checking for palindromes, capitalizing sentences, and counting vowels.
In this document
Powered by AI
Overview of algorithms as step-by-step problem-solving procedures and pseudocode as a language for representing algorithms.
Pseudocode design includes naming conventions and basic keywords used for input/output, control flow, and comments.
Examples of creating pseudocode for basic operations like calculation, checking odd/even, and finding the maximum of numbers.
Using pseudocode to illustrate loops with examples that print numbers sequentially and sum integers.
Algorithm for determining prime numbers, including definitions and checks for divisibility in pseudocode.
Various coding tasks such as reversing integers and strings, finding palindromes, capitalizing sentences, and counting vowels.
Algorithm and psuedocode
- 1. Algorithms & Pseudocode BYM. QURESHI
- 2. A typicalprogramming task can be divided into two phases: Problem solving phase produce an ordered sequence of steps that describe solution of problem this sequence of steps is called an algorithm Implementation phase implement the program in some programming language
- 3. Steps in problemSolving Produce a general Algorithm Refine the algorithm Successively to get step by step detailed algorithm that is very close to a computer language. Pseudocode is an artificial and informal language that helps programmers develop algorithms Pseudocode is very similar to everyday English
- 4. Pseudocode The firstthing we do when designing a program is to decide on a name for the program Let’s say we want to write a program to calculate interest, a good name for the program would be CalculateInterest. Note the use of CamelCase.
- 5. Pseudocode isused to represent the logic of the solution to a problem. Once the pseudocode is verified, it can be converted into a program using the vocabulary and syntax of a programming language Keywords in Pseudocode. Begin … End: these keywords are used to start and finish pseudocode. Begin is the first line and end is the last line of pseudocode. Accept: This keyword is used to obtain an input from a user. Display: this keyword is used to present a result or an output. If .. Else .. End if : These keywords are used in decision-making. //: Comment Do .. While, for … repeat … until : Represent loop
- 6. So we startthe program as : Program CalculateInterest: And in general it’s : Our Program will finish with the following END. PROGRAM <ProgramName>: END.
- 7. So let’s saywe want to express the following algorithm Read in a number and print it out double the number. PROGRAM PrintDoubleNumber: Read A; B = A*2; Print B; End.
- 8. So let’s saywe want to express the following algorithm Read in a number, check if it is odd or even. PROGRAM IsOddOrEven: Read A; If (A/2 gives a remainder) Then Print “Its’s Odd”; Else Print ”It’s Even”; EndIf; End.
- 9. So let’s saywe want to express the following algorithm to print out the bigger of two numbers: Read in two numbers, call them A and B. Is A is bigger than B, print out A, otherwise print out B. PROGRAM PrintBiggerOfTwo: Read A; Read B; If (A>B) Then Print A; Else Print B; EndIf; End.
- 10. So let’s saywe want to express the following algorithm to print out the bigger of three numbers: Read in three numbers, call them A, B and C. If A is bigger than B, then if A is bigger than C, print out A, otherwise print out C. If B is bigger than A, then if B is bigger than C, print out B, otherwise print out C.
- 11. PROGRAM BiggerOfThree: Read A; ReadB; Read C; If (A>B) then If (A>C) Then Print A; Else Print B; End If;(B>C) Then Print B; Else Print C; End If; End If; End.
- 12. So let’s saywe want to express the following algorithm: Print out the numbers from 1 to 5 PROGRAM Print1to5: A=1; WHILE ( A !=6) Do Print A; A= A+1; ENDWHILE; End.
- 13. So let’s saywe want to express the following algorithm: – Add up the numbers 1 to 5 and print out the result PROGRAM PrintSum1to5: Total =0; A=1; WHILE ( A !=6) Do Total = total +A; A= A+1; ENDWHILE; Print Total; End.
- 14. So let’s saywe want to express the following algorithm: – Read in a number and check if it’s a prime number. What’s a prime number? – A number that’s only divisible by itself and 1, e.g. 7. Or to put it another way, every number other than itself and 1 gives a remainder, e.g. For 7, if 6, 5, 4, 3, and 2 give a remainder then 7 is prime. – So all we need to do is divide 7 by all numbers less than it but greater than one, and if any of them have no remainder, we know it’s not prime.
- 15. So, Ifthe number is 7, as long as 6, 5, 4, 3, and 2 give a remainder, 7 is prime. If the number is 9, we know that 8, 7, 6, 5, and 4, all give remainders, but 3 does not give a remainder, it goes evenly into 9 so we can say 9 is not prime. So remember, – if the number is 7, as long as 6, 5, 4, 3, and 2 give a remainder, prime. So, in general, – if the number is A, as long as A-1, A-2, A-3, A4, ... 2 give a remainder, A is prime.
- 16. PROGRAM prime: Read A; B= A-1; IsPrime = True; While(B !=1) DO IF ( A/B gives no remainder) THEN IsPrime = false; End If B=B-1; ENDWHILE; If(IsPrime ==true) Then Print “Prime”; Else Print “Not Prime”; EndIf; End.
- 17. Write Algorithm &Pseudocode & then Actual Code Write a Program to Reverse an Integer // --- Directions // Given an integer, return an integer that is the reverse // ordering of numbers. // --- Examples // reverseInt(15) === 51 // reverseInt(981) === 189 // reverseInt(500) === 5 // reverseInt(-15) === -51 // reverseInt(-90) === -9
- 18. Write a Programto Reverse a String // --- Directions // Given a string, return a new string with the reversed // order of characters // --- Examples // reverse('apple') === 'leppa' // reverse('hello') === 'olleh' // reverse('Greetings!') === '!sgniteerG'
- 19. Write a programto Find Palindromes // --- Directions // Given a string, return true if the string is a palindrome // or false if it is not. Palindromes are strings that // form the same word if it is reversed. *Do* include spaces // and punctuation in determining if the string is a palindrome. // --- Examples: // palindrome("abba") === true // palindrome("abcdefg") === false
- 20. Write a Programthat will capitalize a sentence // --- Directions // Write a function that accepts a string. The function should // capitalize the first letter of each word in the string then // return the capitalized string. // --- Examples // capitalize('a short sentence') --> 'A Short Sentence' // capitalize('a lazy fox') --> 'A Lazy Fox' // capitalize('look, it is working!') --> 'Look, It Is Working!'
- 21. Write a functionthat returns the number of vowels // --- Directions // Write a function that returns the number of vowels // used in a string. Vowels are the characters 'a', 'e' // 'i', 'o', and 'u'. // --- Examples // vowels('Hi There!') --> 3 // vowels('Why do you ask?') --> 4 // vowels('Why?') --> 0