Algorithmic thinking with python Module 1.2
- 1. ► PROBLEM-SOLVING STRATEGIES:- Problem-solving strategies defined, Importance of understanding multiple problem-solving strategies, Trial and Error, Heuristics, Means- Ends Analysis, and Backtracking (Working backward). Page 1 ► THE PROBLEM-SOLVING PROCESS:- Computer as a model of computation, Understanding the problem, Formulating a model, Developing an algorithm, Writing the program, Testing the program, and Evaluating the solution. ► ESSENTIALS OF PYTHON PROGRAMMING:- Creating and using variables in Python, Numeric and String data types in Python, Using the math module, Using the Python Standard Library for handling basic I/O - print, input, Python operators and their precedence. Module 1
- 2. ► Core Concept: Computer science is about solving problems using computers. ► Problem Sources: Problems can be real-world or abstract. ► Key Focus: Understanding the computer's information processing model is crucial. ► Information Processing Model: Typically assumes a single CPU to illustrate data flow. ► Modern Computers: Many have multiple CPUs, enabling parallel processing. ► Systematic Approach: A standardized, systematic approach is essential for effective problem- solving. INTRODUCTION Page 2
- 3. ► Basic Model: Start with input, process it, and produce the desired output. ► Complex Problems: The model must be iterated multiple times for larger problems. ► Intermediate Results: Iteration produces partial solutions that contribute to solving the overall problem. ► Simplicity vs. Complexity: The basic model works for simple tasks, but complex problems require a more iterative approach. Problem-Solving with the Input/Process/Output Model Page 3
- 4. ► Is the sequential process of analysing information related to a given situation and generating appropriate response options. ► In solving a problem, there are some well-defined steps to be followed. ► Example: Calculate the average grade for all students in a class. ► Input: get all the grades … possibly by typing them in via the keyboard or by reading them from a USB flash drive or hard disk. ► Process: add them all up and compute the average grade. ► Output: output the answer to either the monitor, to the printer, to the USB flash drive or hard disk … or a combination of any of these devices. Problem Solving Page 4
- 5. ► Understanding the problem ► Formulating a Model ► Developing an algorithm ► Writing the program ► Testing the program ► Evaluating the Solution Problem Solving - Steps Page 5
- 7. ► The First Step in Problem Solving: Understanding the Problem ► It may sound simple, but the first step in solving any problem is to fully understand it. ► Key Questions: ► What input data/information is available? ► What does the data represent, and in what format? ► Is anything missing from the data? ► Do I have everything needed to solve the problem? ► Example: Grades as Input: ► Grades could be numbers (0-100) or letter grades (A-F). ► Consider how to handle missing grades (e.g., absentees). Understanding the problem
- 8. ► Identifying Output and Processing Needs ► Output Requirements: ► What output is needed, and in what format (text, number, graph)? ► Example: Should the result be a number, a letter grade, or a pie chart? ► Processing Considerations: ► Understand the processing steps required to achieve the desired output. ► This understanding guides the problem-solving process. Understanding the problem
- 10. ► Understanding the Need: ► A model or formula is necessary to compute the average of numbers. ► Fully understanding the input data is key to developing this model. ► Example 1: Numerical Grades: ► Input: Grades as integers or real numbers (e.g., 𝑥1, 𝑥2, ⋯ , 𝑥𝑛).Model: 𝐴𝑣𝑒𝑟𝑎𝑔𝑒1 = (𝑥1 + 𝑥2 + ⋯ + 𝑥𝑛)/𝑛. ► Output: A number from 0 to 100. Formulating a Model
- 11. ► Challenge ► Letter grades (e.g., A, B-, C+) cannot be directly added or divided. ► Solution ► Assign Values: Convert letter grades to numerical equivalents (e.g., A+ = 12, F = 0). ► Model: 𝐴𝑣𝑒𝑟𝑎𝑔𝑒2 = (𝑦1 + 𝑦2 + ⋯ + 𝑦𝑛)/𝑛.Output: A number from 0 to 12.Final ► Output: Convert 𝐴𝑣𝑒𝑟𝑎𝑔𝑒2 to a percentage or map it back to a letter grade using a lookup table. ► Key Insight: The goal is to use available data effectively to compute the desired result. Formulating a Model
- 13. Developing an algorithm ► An algorithm is a set of steps for solving a particular problem. ► The set of steps in an algorithm must be unambiguous and have a clear stopping point. ► Algorithm can written in any natural language like English. ► An algorithm has the following properties: ► Finiteness - the process terminates, the number of steps are finite ► Definiteness - each step is precisely stated ► Effective computability - each step can be carried out by a computer
- 14. Do you know Over 1,000 years before the internet and smartphone apps, Persian scientist and polymath Muhammad ibn Mūsā al- Khwārizmī invented the concept of algorithms. In fact, the word itself comes from the Latinised version of his name, “algorithmi”. Source: https://en.wikipedia.org/wiki/Algorithm
- 15. Different Patterns in Algorithm ► An algorithm has different patterns(constructs in it) ► Sequential ► is progression of tasks or statements that follow one after the other. ► Conditional ► Different steps are executed based on a condition ► Iterational ► A task( one or more steps) is repeated more than once ► It is also known as repetitive construct
- 16. Using Algorithms to Solve Problems Identify the inputs and outputs Identify any other data and constants required to solve the problem Identify what needs to be computed Write the algorithm
- 17. Using Algorithms to Solve Problems Problem Statement: Find the average of three numbers ► Identify the inputs and outputs ► The above problem statement, average of three numbers is the desired output. Here the three numbers are the inputs. ► Identify any other data and constants required to solve the problem ► The average of numbers is defined as: ► Sum of all inputs / total number of inputs ► Here the other data to be computed is the sum. The total number of inputs is ‘3’, which is a constant in this case.
- 18. Using Algorithms to Solve Problems Problem Statement: Find the average of three numbers ► Identify what needs to be computed ► Problem Statement: Find the average of three numbers ► It is clear that the average of three numbers has to be computed
- 19. Using Algorithms to Solve Problems Problem Statement: Find the average of three numbers ► Write an algorithm Step 1: Start Step 2: Read three numbers and store values as Number1, Number2 and Number 3 Step 3: Add three numbers and store the value as Sum Step 4: Divide the Sum by 3 to calculate the average Step 5: Display Average Step 6: End
- 20. Page 22 Writing the Program
- 21. Writing the Program ► Coding/Implementing an Algorithm: The process of transforming an algorithm into a set of instructions that a computer can understand is called coding or implementing an algorithm. ► Source Code: The program itself, written in a programming language, is referred to as the source code.
- 22. Writing the Program ► The computer requires precise instructions in order to understand what it is being asked to do. ► For example, removing one of the semi- colon characters (“) from the program above, will make the computer become confused as to what it’s being asked to do
- 23. Good Coding Practices ► Write Clear and Descriptive Comments ► Use comments to explain the purpose of the code, especially for complex logic. ► Use Meaningful Variable and Function Names ► Choose descriptive names that reflect the role of the total_sum , variable or function (e.g., calculate_average). ► Keep Code DRY (Don’t Repeat Yourself) ► Avoid duplicating code by reusing functions and logic whenever possible. ► Consistent Code Formatting ► Use consistent indentation, spacing, and line breaks for better readability.
- 24. Good Coding Practices ► Write Modular Code ► Break your program into smaller, reusable functions or modules that perform specific tasks. ► Avoid Magic Numbers ► Replace hard-coded numbers with named constants for better clarity (e.g., MAX_LIMIT = 100). ► Optimize for Readability Over Cleverness ► Write code that is easy to understand, rather than trying to be overly clever or complex. ► Follow Coding Standards ► Adhere to industry-specific coding guidelines like PEP 8 for Python or the coding style guide for your language.
- 25. Test the Program
- 26. Test the Program ► After writingand compiling a program, the next step is to verify if it solves the intended problem. ► Running a program means instructing the computer to execute the compiled code. ► Correct results indicate the program is functioning properly, but issues may arise with certain inputs. ► Incorrect results can stem from: ► Improper conversion of the algorithm into code. ► A flawed algorithm that doesn’t handle all situations. ► Instructions executed in the wrong order. ► These issues are referred to as bugs.
- 27. Test the Program ► Bugs: Errors in a program causing it to fail or produce incorrect/undesirable results. ► Fixing bugs is the programmer’s responsibility. ► Use multiple test cases to find bugs, forming a test suite. ► Debugging: The process of finding and fixing errors in code. ► Debugging can be time-consuming but is essential for ensuring a program works as expected. ► Following careful steps during problem analysis, algorithm design, and coding reduces bugs. ► This results in an easier and more efficient debugging process.
- 28. Test the Program ► Bug in Summing: The program mistakenly sums only num1 and num2, leaving out num3. ► This leads to an incorrect total. ► Incorrect Division: The program then divides this incorrect sum by 3, which produces an incorrect average. ► Result: Expected Result: The average should be (10 + 20 + 30) / 3 = 20. ► Buggy Output: The program will output (10 + 20) / 3 = 10, which is incorrect because it didn't include num3 in the sum.
- 29. Test the Program ► Understand the Program: ► Review the program’s purpose: to calculate the average of three numbers. ► Run the Program: ► Execute the program with the given values (num1 = 10, num2 = 20, num3 = 30). ► Note the output. It should display the average. ► Check Expected Output: ► Calculate the expected average manually: ► Compare Outputs: ► Compare the program's output to the expected average. ► Identify any discrepancies (e.g., if the output is 10 instead of 20).
- 30. Test the Program ► Review the Code: ► Examine the lines where calculations are performed: ► Check how total_sum is computed. ► Ensure that all intended variables (num1, num2, and num3) are included in the calculation. ► Identify the Bug: ► Notice that the calculation for total_sum is missing num3: ► This indicates that the bug lies in the way the total is calculated. ► Fix the Bug: ► Modify the code to include num3 in the sum: ► Test Again: ► Return the program after the fix. Verify that the output now matches the expected average of 20.
- 31. Page 33 Evaluating the Solution
- 32. Evaluating the Solution ► Once a program produces a result, revisit the original problem. ► Ensure the output is formatted as a proper solution. ► Examine if the result aligns with the original intent. ► Determine if the output meets the problem's requirements. ► Remember that the computer executes instructions as given. The user must interpret results to determine effectiveness.
- 34. Page 36 Thank You Prof. Sarju S Department of Computer Science and Engineering St. Joseph’s College of Engineering and Technology, Palai (Autonomous) [email protected] Disclaimer - This document contains images/texts from various internet sources. Copyright belongs to the respective content creators.