Building blocks of Algblocks of Alg.pptx
- 1. UNIT I Building Blocks of Algorithms Dr. Nisha Soms, AP(Sr.Gr.)/CSE UCSG004 Python Programming for Engineers
- 2. PROBLEM SOLVING Problem solving is a systematic approach to define the problem and creating number of solutions. The problem solving process starts with the problem specifications and ends with a correct program. PROBLEM SOLVING TECHNIQUES Problem solving technique is a set of techniques that helps in providing logic for solving a problem. Problem solving can be expressed in the form of 1. Algorithms. 2. Flowcharts. 3. Pseudo codes. 4. Programs 18-01-2024 2
- 3. THE PROBLEM SOLVING ASPECT 18-01-2024 3 Is a creative process that involves the following phases Problem Definition Phase Getting started on a problem The use of specific examples Similarities among problems Working backwards from solutions
- 4. ALGORITHMS An algorithm is a procedure consisting of a finite set of unambiguous rules (instructions) which specify a finite sequence of operations that provides the solution to a problem. OR A sequence of activities to be processed for getting desired output from a given input. OR Formal Definition: An algorithm is a finite number of clearly described, unambiguous “double” steps that can be systematically followed to produce a desired result for the given inputs in a finite amount of time. 18-01-2024 4
- 5. ALGORITHMS 18-01-2024 5 Convert temperature Fahrenheit to Celsius Inputs to the algorithm: Temperature in Fahrenheit Expected output: Temperature in Celsius Algorithm: Step1: Start Step 4: Read Temperature in Fahrenheit F Step 2: C = 5/9*(F*32) Step 3: Print Temperature in Celsius: C Step5: End
- 6. BUILDING BLOCKS OF ALGORITHMS/TYPES 18-01-2024 6 Building Block Common name Sequence Action Selection Decision Iteration Repetition or Loop In a sequence structure, an action, or event, leads to the next ordered action in a predetermined order. In a selection structure, a question is asked, and depending on the answer, the program takes one of two courses of action, after which the program moves on to the next event An iteration is a single pass through a group/set of instructions. Most programs often contain loops of instructions that are executed over and over again.
- 7. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 7 Statements: Statement is a single action in a computer. In a computer statements might include some of the following actions input data-information given to the program process data-perform operation on a given input output data-processed result
- 8. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 8 State: Transition from one process to another process under specified condition with in a time is called state. Control flow: The process of executing the individual statements in a given order is called control flow. The control can be executed in three ways Sequence Selection Iteration
- 9. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 9 Sequence: All the instructions are executed one after another is called sequence execution. Example: Add two numbers: Step 1: Start Step 2: get a,b Step 3: calculate c=a+b Step 4: Display c Step 5: Stop
- 10. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 10 Selection: A selection statement causes the program control to be transferred to a specific part of the program based upon the condition. If the conditional test is true, one part of the program will be executed, otherwise it will execute the other part of the program.
- 11. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 11 Example Write an algorithm to check whether he is eligible to vote? Step 1: Start Step 2: Get age Step 3: if age >= 18 print “Eligible to vote” Step 4: else print “Not eligible to vote” Step 6: Stop
- 12. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 12 Iteration: In some programs, certain set of statements are executed again and again based upon conditional test. i.e. executed more than one time. This type of execution is called looping or iteration. Example Write an algorithm to print all natural numbers up to n Step 1: Start Step 2: get n value. Step 3: initialize i=1 Step 4: if (i<=n) go to step 5 else go to step 7 Step 5: Print i value and increment i value by 1 Step 6: go to step 4 Step 7: Stop
- 13. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 13 Functions: Function is a sub program which consists of block of code(set of instructions) that performs a particular task. For complex problems, the problem is been divided into smaller and simpler tasks during algorithm design. Benefits of Using Functions Reduction in line of code code reuse Better readability Information hiding Easy to debug and test Improved maintainability
- 14. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) 18-01-2024 14 Algorithm for addition of two numbers using function Main function() Step 1: Start Step 2: Call the function add() Step 3: Stop sub function add() Step 1: Function start Step 2: Get a, b Values Step 3: add c=a+b Step 4: Print c Step 5: Return