py_1.pdf

GE8151 PROBLEM SOLVING AND PYTHON PROGRAMMING UNIT I ALGORITHMIC PROBLEM SOLVING Algorithms, building blocks of algorithms (statements, state, control flow, functions), notation (pseudo code, flow chart, programming language), algorithmic...

GE8151 PROBLEM SOLVING AND PYTHON PROGRAMMING UNIT I ALGORITHMIC PROBLEM SOLVING Algorithms, building blocks of algorithms (statements, state, control flow, functions), notation (pseudo code, flow chart, programming language), algorithmic problem solving, simple strategies for developing algorithms (iteration, recursion). Illustrative problems: find minimum in a list, insert a card in a list of sorted cards, Guess an integer number in a range, Towers of Hanoi. 1.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. 1.1 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 1.2.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  Should be written in simple English  Each and every instruction should be precise and unambiguous.  Instructions in an algorithm should not be repeated infinitely.  Algorithm should conclude after a finite number of steps.  Should have an end point  Derived results should be obtained only after the algorithm terminates. 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. Unit 1: Algorithmic problem solving 1 Example: Example Write an algorithm to print „Good Morning” Step 1: Start Step 2: Print “Good Morning” Step 3: Stop 2.BUILDING BLOCKS OF ALGORITHMS (statements, state, control flow, functions) Algorithms can be constructed from basic building blocks namely, sequence, selection and iteration. 2.1.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 2.2.State: Transition from one process to another process under specified condition with in a time is called state. 2.3.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 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 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. Unit 1: Algorithmic problem solving 2 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 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