Python Algorithmic Problem Solving: brief important questions and answers

1. What are the building blocks of an algorithm? Explain in detail.

The building blocks of algorithm are -Statements

-State

-Control flow

-Functions

Statements:

There are 3 types of statements:

-Input/Output Statement

-Assignment Statement

-Control Statement

State:

There are 3 types of state:

-Initial state

-Current state

-Final state

Control flow:

-Sequence

The sequence structure is the construct where one statement is executed after another -Selection

The selection structure is the construct where statements can executed or skipped depending on whether a condition evaluates to TRUE or FALSE. There are three selection structures in C:

1.             IF

2.             IF – ELSE

3.             SWITCH

Repetition

The repetition structure is the construct where statements can be executed repeatedly until a condition evaluates to TRUE or FALSE. There are two repetition structures in C:

1.             WHILE

2.             FOR

Functions:

A function is a block of organized reusable code that is used to perform a single action.

2. Briefly describe iteration and recursion. Illustrate with an example.

Example: Iterative algorithm for factorial of a number

Example: Recursive algorithm for factorial of number

3. Explain in detail Algorithmic problem solving.

4. Write an algorithm and draw a flowchart to calculate 2⁴.

Algorithm:

Step 1: Start

Step 2: Initialize the value of result, r=1.

Step 3: Repeat step4 for 4 times

Step 4: calculate r=r*2

Step 5: Print the value of r

Step 6: Stop

Flowchart:

5. a) Describe pseudo code with its guidelines.

Pseudo code consists of short, readable and formally-styled English language used for explaining an algorithm. Pseudo code does not include details like variable declarations, subroutines etc.

Preparing a Pseudo Code

·                 Pseudo code is written using structured English.

·                 In a pseudo code, some terms are commonly used to represent the various actions. For example,

for inputting data the terms may be (INPUT, GET, READ),

for outputting data (OUTPUT, PRINT, DISPLAY),

for calculations (COMPUTE, CALCULATE),

for incrementing (INCREMENT),

in addition to words like ADD, SUBTRACT, INITIALIZE used for addition, subtraction, and initialization, respectively.

·                 The control structures—sequence, selection, and iteration are also used while writing the pseudo code.

·                 The sequence structure is simply a sequence of steps to be executed in linear order.

·                 The selection constructs—if statement and case statement. In the if-statement, if the condition is true then the THEN part is executed otherwise the ELSE part is executed. There can be variations of the if-statement also, like there may not be any ELSE part or there may be nested ifs. The case statement is used where there are a number of conditions to be checked. In a case statement, depending on the value of the expression, one of the conditions is true, for which the corresponding statements are executed. If no match for the expression occurs, then the OTHERS option which is also the default option, is executed.

·                 WHILE and FOR are the two iterative statements.

b) Give an example for pseudo code.

Pseudocode for finding maximum in a list:

BEGIN

SET numlist=[ ]

GET n

FOR i=1 to n

GET numlist elements

ENDFOR

SET maximum = numlist[0]

FOR i in numlist

IF (n > maximum)

maximum = n

ENDIF

ENDFOR

PRINT maximum

END

c) Write the pseudo code for Towers of Hanoi.

Pseudocode

START

Procedure Hanoi(disk, source, dest, aux)

IF disk = = 0, THEN

move disk from source to dest

ELSE

Hanoi(disk - 1, source, aux, dest)

move disk from source to dest

Hanoi(disk - 1, aux, dest, source)

END IF

END Procedure

6. a) What is flowchart?

Flowchart is a diagrammatic representation of the logic for solving a task. A flowchart is drawn using boxes of different shapes with lines connecting them to show the flow of control. The purpose of drawing a flowchart is to make the logic of the program clearer in a visual form.

b) List down symbols and rules for writing flowchart.

c) Draw a flowchart to count and print from1 to 10.

7. a) Write an algorithm and give the flowchart to find the net salary of an employee.

Algorithm:

Step 1: Start

Step 2 : Read the basic salary

Step 3 : IF the basic is greater than or equal to 4000 ELSE Goto Step 4

Step 3.1 : DA= 0.32 * basic (Dearness Allowance)

Step 3,2 : HRA = 0.15 * basic (House Rent Allowance)

Step 3.3 : CCA = 325 (City Compensatory Allowance)

Step 3.4 : Net Salary     basic + DA HRA + CCA

Step 4 : Print the Net Salary

Step 5 : Stop

b) Write an algorithm and give the pseudo code to guess an integer number in a range.

Algorithm:

step 1: Start the program

step 2: Read an 'n' number

step 3: Read an Guess number

step 4: if Guess> n; print "Your Guess too high" Step 5: elif Guess <n ; print "Your Guess

too low" step 6: elif Guess = = n; print "Good job"

Step 7: else print"Nope "

Step :8 Stop the program

Pseudocode:

BEGIN

READ n

READ Guess = 20

IF Guess> n

print"Your Guess too High" elif Guess< n

print "Your Guess too low" elif Guess = = 20

print "Good Job"

ELSE

print"Nope"

8. a) Write an algorithm to insert a card in a list of sorted cards.

ALGORITHM:

Step 1: Start

Step 2: Declare the variables N, List[],I and X

Step 3: READ Number of element in sorted list as N

Step 4: SET i=0

Step 5: IF i<N THEN go to step 6 ELSE go to step 9

Step 6: READ Sorted list element as List[i]

Step 7: i=i+1

Step 8: go to step 5

Step 9: READ Element to be insert as X

Step 10: SET i=N-1

Step 11: IF i>0 AND X<List[i] THEN go to step 12 ELSE go to step 15

Step 13: i=i-1

Step 14: go to step 11

Step 15: List[i+1]=X

Step 16: Stop

b) Write an algorithm to find the minimum number in a list.

Algorithm:

Step 1 : Start

Step 2 : Initialize the value of minimum = 0

Step 3 : Enter the input number (n) of items in a list.

Step 4 : Get all the elements using for loop and store it in a list.

Step 5: Assign the first element in a list as minimum.

Step 6: Compare maximum with the first element in a list,n.

Step 7: Repeat step 8,9 until list becomes empty.

Step 8 : If n is less than the minimum

Step 9 : Assign minimum = n

Step 10 : Display mi nimum

Pseudocode:

BEGIN

SET numlist=[ ]

GET n

FOR i=1 to n

GET numlist elements

ENDFOR

SET minimum = numlist[0]

FOR i in numlist

IF (n < minimum)

minimum = n

ENDIF

ENDFOR

PRINT minimum

END

BART B:

1.              Explain in detail about problem solving techniques?

2.              Explain in detail about building blocks of algorithm?

3.              Discuss the symbols and rules for drawing flowchart with the example?

4.              Explain in detail about programming language?

5.              Discuss briefly about algorithmic problem solving?

6.              Write algorithm, pseudo code and flow chart for any example?

7.              Explain in detail about simple strategies for developing algorithms?