Assignment 4 Find a hidden sentence in a book.

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Assignment 4
Objective: Find a hidden sentence in a book.
An old way of secret communication is to construct sentences from the words in a
book. The sender and receiver agree on a book and the sender provides the receiver
with instructions for extracting the sentence from the book. Your program’s job is to
get a text file that contains the book and a text file that contains the instructions, and
the hidden sentence by following the instructions, and print it.
Your program that takes two command line arguments:
• The name of the file that contains the book. You can assume that there will be
at most 10000 lines in the file, and that each line will be at most 200 characters
• The name of the file that contains the instructions. Each line in the file describes
an instruction.
Each instruction specifies how to extract the next word. The first instruction gives the
index of the line and the index of the word within the line. Note that both indexes are
1-based (not 0-based). Subsequent instructions specify the offset of the next line
(positive offsets move forward, negative offsets move backward) and the index of the
word in that line. For example if the instruction lines are 5 2, 2 4, -3 1, the words to
be selected are: line 5 word 2, line 7 word 4, line 4 word 1.
Your program will read both files and store the data in two arrays. To represent the
book, use a char** (an array of strings). To represent the instructions, use a struct
instruction_s* where each instruction is represented by the following struct type:
struct instruction_s {
int step; int index;
The step specifies the offset of the next line and the index specifies the index of the
word in the line.
Write the following functions to accomplish your task:
• A function get_word that takes a line s and an index n, and returns the selected
word. This function should have the following signature:
char* get_word(char* s, int n)
• A function that takes the lines of a book, a sequence of instructions, the number
of instructions n_instructions, and an empty sentence where to store the
extracted sentence. This function should have the signature:
void get_sentence(char** lines, struct instruction_s* instructions, int
n_instructions, char* sentence)
As you are processing the text, you have to remove all punctuation marks attached to
the words (e.g. hi! should be converted to hi ) and convert all upper case letters to
lower case (e.g. Hi! should be converted to hi).
You can assume that the instructions will not result in locations that do not exist in
the text.
Two files have been provided for testing your code: The alice.txt le contains the novel
Alice’s Adventures in Wonderland taken from Project Gutenberg, and the
instructions.txt contains an example sequence of instructions. Below is an example
./assignment4 alice.txt instructions.txt
fight for your right to party
Although not required in this assignment, you are strongly recommended to run your
program under valgrind to spot any memory issues. Unfortunately valgring is not
installed in the system that we access using SSH. An example run using valgrind is as
valgrind –leak-check=full ./assignment4 alice.txt instructions.txt
• Make sure to properly document your functions (purpose, parameters, etc.) as
shown in the class and the slides.
• Your source code file has to have the name assignment4.c .
• Your program will be compiled using the following command on a Linux system.
If it cannot be compiled and linked using this command, it will not be graded
(failed submission).
gcc -std=c99 -Wall -Werror assignment4.c -o assignment4
• Your program will be checked using an automatic checker. Therefore, make sure
you print the messages exactly as given in the example runs and check your
code using given test file.
• You can use string library functions and file I/O functions.
• Do NOT use any C++ features such as cout and cin.
• Make sure your coding style is proper and consistent. Use the clang-format tool
if necessary. Don’t use any variable names in a language other than English.
• This is an individual assignment. Collaboration in any form is NOT allowed. No
working together, no sharing code in any form including showing code to your
classmates to give them ideas.
• All the code you submit must be your own. Don’t copy/paste any piece of code
from any resource including anything you’ve found on the Internet.
• The assignments will be checked for plagiarism using both automated tools and
manual inspection. Any assignment involving plagiarism and/or infringement of
intellectual property will be not be graded and is subject to further disciplinary


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