Introduction to problem solving Techniques
- 1. PROBLEM SOLVING USING PYTHON INTRODUCTION Prepared By, Dr. S. Beulah / ASP/ NICHE Ms. M. MERLIN JOHNSY / AP/ NICHE
- 2. PROBLEM SOLVING Problem solving is the 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
- 3. PROBLEM SOLVING TECHNIQUES Problem solving technique is a set of techniques that helps in providing logic for solving a problem. Problem Solving Techniques: Problem solving can be expressed in the form of 1. Algorithms. 2. Flowcharts. 3. Pseudo codes. 4. programs
- 4. Algorithm Flowchart Pseudo code Step by step process written in normal English language to solve the given problem. Diagrammatic representation of the solution Similar to program. Pseudo – False Code - Program Step 1 : Start . . . Step n :Stop Input – READ, OBTAIN, GET, PROMPT Output – PRINT, DISPLAY, SHOW Compute – COMPUTE, CALCULATE, DETERMINE Initiate - SET, INITIALIZE Add One – INCREMENT
- 5. ALGORITHM It is defined as a sequence of instructions that describe a method for solving a problem. In other words it is a step by step procedure for solving a problem. Properties of Algorithms v Should be written in simple English v Each and every instruction should be precise and unambiguous. v Instructions in an algorithm should not be repeated infinitely. v Algorithm should conclude after a finite number of steps. v Should have an end point v Derived results should be obtained only after the algorithm terminates.
- 6. Qualities of a good algorithm The following are the primary factors that are often used to judge the quality of the algorithms. Time – To execute a program, the computer system takes some amount of time. The lesser is the time required, the better is the algorithm. Memory – To execute a program, computer system takes some amount of memory space. The lesser is the memory required, the better is the algorithm. Accuracy – Multiple algorithms may provide suitable or correct solutions to a given problem, some of these may provide more accurate results than others, and such algorithms may be suitable. Example Write an algorithm to print „Good Morning” Step 1: Start Step 2: Print “Good Morning” Step 3: Stop
- 7. BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) Algorithms can be constructed from basic building blocks namely, sequence, selection and iteration. Statements: Statement is a single action in a computer. In a computer statements might include some of the following actions Ø input data-information given to the program Ø process data-perform operation on a given input Ø output data-processed result 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 1. sequence 2. selection 3. iteration
- 8. 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
- 9. 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. 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
- 10. 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
- 11. Functions: v Function is a sub program which consists of block of code(set of instructions) that performs a particular task. v For complex problems, the problem is been divided into smaller and simpler tasks during algorithm design. Benefits of Using Functions v Reduction in line of code v code reuse v Better readability v Information hiding v Easy to debug and test v Improved maintainability
- 12. Example: 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
- 13. NOTATIONS FLOW CHART • Flow chart is defined as graphical representation of the logic for problem solving. • The purpose of flowchart is making the logic of the program clear in a visual representation.
- 14. Rules for drawing a flowchart 1. The flowchart should be clear, neat and easy to follow. 2. The flowchart must have a logical start and finish. 3. Only one flow line should come out from a process symbol. 4. Only one flow line should enter a decision symbol. However, two or three flow lines may leave the decision symbol.
- 15. 5. Only one flow line is used with a terminal symbol. 6. Within standard symbols, write briefly and precisely. 7. Intersection of flow lines should be avoided.
- 16. Advantages of flowchart: 1. Communication: - Flowcharts are better way of communicating the logic of a system to all concerned. 2. Effective analysis: - With the help of flowchart, problem can be analysed in more effective way. 3. Proper documentation: - Program flowcharts serve as a good program documentation, which is needed for various purposes. 4. Efficient Coding: - The flowcharts act as a guide or blueprint during the systems analysis and program development phase. 5. Proper Debugging: - The flowchart helps in debugging process. 6. Efficient Program Maintenance: - The maintenance of operating program becomes easy with the help of flowchart. It helps the programmer to put efforts more efficiently on that part.
- 17. Disadvantages of flow chart: 1. Complex logic: - Sometimes, the program logic is quite complicated. In that case, flowchart becomes complex and clumsy. 2. Alterations and Modifications: - If alterations are required the flowchart may require re-drawing completely. 3. Reproduction: - As the flowchart symbols cannot be typed, reproduction of flowchart becomes a problem. 4. Cost: For large application the time and cost of flowchart drawing becomes costly.
- 18. STEP1: START STEP2: Get n value STEP 3: if n % 2==0 then GOTO STEP 4 ,otherwise GOTO STEP 5 STEO4: PRINT N is EVEN number STEP 5: PRINT N is ODD number STEP6: STOP
- 19. PSEUDO CODE: ■ Pseudo code consists of short, readable and formally styled English languages used for explain an algorithm. ■ It does not include details like variable declaration, subroutines. ■ It is easier to understand for the programmer or non programmer to understand ■ the general working of the program, because it is not based on any programming language. ■ It gives us the sketch of the program before actual coding. ■ It is not a machine readable ■ Pseudo code can’t be compiled and executed. ■ There is no standard syntax for pseudo code.
- 20. Guidelines for writing pseudo code: ■ Write one statement per line ■ Capitalize initial keyword ■ Indent to hierarchy ■ End multiline structure ■ Keep statements language independent
- 21. Common keywords used in pseudocode The following gives common keywords used in pseudocodes. 1. //: This keyword used to represent a comment. 2. BEGIN,END: Begin is the first statement and end is the last statement. 3. INPUT, GET, READ: The keyword is used to inputting data. 4. COMPUTE, CALCULATE: used for calculation of the result of the given expression. 5. ADD, SUBTRACT, INITIALIZE used for addition, subtraction and initialization. 6. OUTPUT, PRINT, DISPLAY: It is used to display the output of the program. 7. IF, ELSE, ENDIF: used to make decision. 8. WHILE, ENDWHILE: used for iterative statements. 9. FOR, ENDFOR: Another iterative incremented/decremented tested automatically.
- 23. EVEN/ODD Num=int(“Enter any value”) IF(num%2==0) PRINT(“ num even number”) ELSE PRINT (“num odd number”)
- 24. Advantages: ■ Pseudo is independent of any language; it can be used by most programmers. ■ It is easy to translate pseudo code into a programming language. ■ It can be easily modified as compared to flowchart. ■ Converting a pseudo code to programming language is very easy as compared with converting a flowchart to programming language.
- 25. Disadvantages: ■ It does not provide visual representation of the program’s logic. ■ There are no accepted standards for writing pseudo codes. ■ It cannot be compiled nor executed. ■ For a beginner, It is more difficult to follow the logic or write pseudo code as compared to flowchart.
- 26. Example: Addition of two numbers: BEGIN GET a,b ADD c=a+b PRINT c END