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Vinay's blog on pragmatic programming for ICSE/ISC students

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Base - ISC Computer Science Practical 2004

Base – ISC Computer Science Practical 2004

The following question was asked in ISC Computer Science Practical (Paper 2) Examination in 2004. The question originally appeared in ACP-ICPC. Source.

Find the base

Numbers have different representations depending on the bases on which they are expressed. For example, in base 3, number 12 is written as 110 but in base 8 it is written as 14.

For this problem your program will presented with a…

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Plotting a sine graph in text mode

Plotting a sine graph in text mode

The purpose of this post is to demonstrate plotting of graphs in text mode using printable character. I would be taking a simple case in which the x-axis is aligned vertically, like shown in the adjoining figure, because cursor cannot move up in the text mode. However, the same can be aligned horizontally by using a double dimension array to first store the plot and then display it using nested…

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ISC Computer Practical 2015 Question 3

ISC Computer Practical 2015 Question 3

Write a program to accept a sentence which may be terminated by either ‘.’ or ‘?’ only. The words are to be separated by a single blank space. Print an error message if the input does not terminate with ‘.’ or ‘?’. You can assume that no word in the sentence exceeds 15 character, so that you get a proper formatted output. Perform the following tasks:

(i) Convert the first letter of each word to…

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ISC Computer Practical 2015 Question 2

ISC Computer Practical 2015 Question 2

Write a program to declare a square matrix A[][] of order MxM where ‘M’ is the number of rows and the number of coloumns, such that M is greater than 2 and less than 10. Accept the value of M as user input. Display an appropriate message for invalid input. Allow the user to input integers into this matrix. Perform the following tasks:

(a) Display the original matrix.

(b) Rotate the matrix 90…

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ISC Computer Practical 2015 Question 1

ISC Computer Practical 2015 Question 1

Given two positive numbers M and N, such that M is between 100 and 10000 and N is less than 100. Find the smallest integer that is greater than M and whose digits add up to N. For example, if M=100 and N=11, then the smallest integer greater than 100 whose digits add up to 11 is 119.

Write a program to accept the numbers M and N from the user and print the smallest required number whose sum of…

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Pangram (holoalphabetic) detection A pangram (Greek: pan gramma, "every letter") or holoalphabetic sentence for a given alphabet is a sentence using every letter of the alphabet at least once. 

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Unique number

A unique number can be defined as a positive integer without leading zeros, in which each digit occurs only once (no duplicate digit). There can be various methods to detect whether or not a given positive integer is a unique number or not. I won’t be discussing methods which requires the number to be converted into a string as that would be inefficient in terms of space and time.

The approach…

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Single character identifiers The objective of this post is to determine the number of single character identifiers which can be constructed in the Java programming language.

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Spiral matrix

In this post I would be discussing the implementation of a program to fill a square double dimension array in a circular fashion, also known as spiral matrix due to it’s appearance. This problem on cyclic filling of an array was asked in the ISC Computer Science Practical Examination 1998.

The problem can be easily solved, if we break it into four parts, one for each direction. We will have one…

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Non-inheritable and non-instantiable class

In this post we would see how to design a class which can neither be instantiated nor inherited. Java language has two modifiers/keywords which provide the individual functionality. A class declared as final cannot be inherited and a class declared as abstract cannot be instantiated. It may seem that if we combine the two we would get a class which is Non-inheritable and non-instantiable, but, if…

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Lucky numbers using recursion

Lucky numbers using recursion

In number theory, a lucky number is a natural number in a set which is generated by a “sieve” similar to the Sieve of Eratosthenes that generates the primes. In my last post I demonstrated an easy method for generating lucky numbers in Java. The last solution was using an iterative technique. In this post we would see a method for generating lucky numbers using recursion.

An animation…

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Lucky numbers

In number theory, a lucky numberis a natural number in a set which is generated by a “sieve” similar to the Sieve of Eratosthenes that generates the primes. In this post I would demonstrate an easy method for generating lucky numbers in Java. The emphasis would be  more on elegance than complex/clever code and therefore we would be using an extra array to reduce the number of loops in the…

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Reversal using recursion

In this post I would be discussing reversal using recursion. Our objective is to reverse a positive integer using a recursive technique. Since I consider using of a global variable (that variable outside the function) as a bad programming practise, our recursive function would be using two arguments. One argument would be for the number to be reversed and the other argument would be for the…

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Evaluation of postfix expression

Evaluation of postfix expression

This post deals with the evaluation of postfix expression also known as reverse polish notation. Please refer to the wikipedia page for the details like advantages and examples. The algorithm essentially is:

While there are input tokens left

Read the next token from input.

If the token is a value

Push it onto the stack.

Otherwise, the token is an operator (operator here includes both operators…

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Linked list

In computer science, a linked listis a data structure consisting of a group of nodes which together represent a sequence. Under the simplest form, each node is composed of a datum and a reference (in other words, a link) to the next node in the sequence; more complex variants add additional links. This structure allows for efficient insertion or removal of elements from any position in the…

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Swap

In this post I be  three popular techniques to swap the values of two variables.

Swap

To swap two variables means to interchange their values. In this post we will see three methods to swap the contents of two variables, viz. using a third variable, using addition/subtraction operator and XOR swap.

Swap the contents of two variables using a third variable

This is the simplest and the most…

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Transpose of a matrix

Transpose of a matrix

In this post I would be discussing a method to determine the transpose of a matrix. The transpose AT of a matrix A can be obtained by reflecting the elements along its main diagonal. In other words, transpose of a matrix means to interchange the rows and columns of a matrix. Repeating the process on the transposed matrix returns the elements to their original position.

transpose of a matrix

Pleas…

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