Add week9 homework

Author: last-genius

weeks/week9/cheatsheet.md

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+## Compilation
+
+After setting up your IDE (VS Code, JetBrains CLion, Vim are among many 
+of the options available) and having your program ready, you have to compile it
+(i.e. turn the text of the program into a machine code which your computer will
+be able to run later).
+
+This can be done like this, in your terminal:
+```
+gcc programname.c -o outputname
+```
+
+If there were errors or notes during the compilation process, the compiler 
+(here we are using the GCC compiler) will notify you. If the program compiled 
+correctly, you can later run the generated executable:
+```
+./outputname
+```
+
+## General tutorial
+
+### Code
+
+Code for execution goes into files with “.c” suffix.  Shared decl’s 
+(included using #include “mylib.h”) in “header” files, end in “.h”
+
+### Comments
+
+Characters to the right of `//` are not interpreted; they’re a comment. 
+Text between `/*` and `*/` (possibly across lines) is commented out as well. 
+
+### Data types 
+
+* `char` - an ASCII value: e.g. ‘a’ (see: man ascii)
+* `int` - a signed integer: e.g. 97 or hex 0x61, oct 0x141  
+* `float` - a floating-point (possibly fractional) value  
+* `double` - a double length float 
+
+`char`, `int`, and `double` are most frequently and easily used in small 
+programs.
+
+sizeof(double) computes the size of a double in bytes.
+
+Zero values represent logical false, nonzero values are logical true.
+
+### Functions
+
+A function is a pointer to some code, parameterized by formal parameters, 
+that may be executed by providing actual parameters. Functions must be 
+declared before they are used, but code may be provided later. 
+
+A `sqrt` function for positive `n` might be declared as:  
+
+```
+int addNumbers(int a, int b)         // function definition with return type, name and parameters
+{
+    int result;
+    result = a+b;
+    return result;                  // return statement
+}
+Functions that do not return anything return `void`.
+There must always be a main function that returns an int:
+```c
+int main() 
+{
+	return 0;
+}
+```
+
+### Statements
+
+Angle brackets identify syntactic elements and don’t appear in real 
+statements
+
+```c
+<expression> ; //semicolon indicates end of a simple statement  
+break; //quits the tightest loop or switch immediately  
+continue; //jumps to next loop test, skipping rest of loop body  
+return x; //quits this function, returns x as value  
+if (<condition>) <stmt>! //stmt executed if cond true (nonzero)  
+if (<condition>) <stmt> else <stmt> // two-way condition  
+while (<condition>) <stmt>    //repeatedly execute stmt only if condition true  
+do <stmt> while (<condition>); //note the semicolon, executes at least once
+for (<init>; <condition>; <step>) { <statements> }
+```
+
+### Includes
+
+The homework requires you to include several header files with the needed functions:
+
+#### I/O (`#include <stdio.h>`)
+Default input comes from “stdin”; output goes to “stdout”; errors to “stderr”.
+Standard input and output routines are declared in `stdio.h`: `#include <stdio.h>`
+* `scanf(p,...)` - reads ... args using format p (below); 
+* `printf(p, ...)` - write ... args using format p (below); pass args as is  fprintf(f,p,...)  
+
+Format specifiers:
+`%c` - character
+`%d` - decimal integer 
+`%s` - string
+`%f` - float
+
+#### MEMORY (`#include <stdlib.h>`)
+* `malloc(n)` - allocates `n` bytes of memory; (for type T: `p = (T*)malloc`)

weeks/week9/homework.md

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+There is a short introduction and cheat sheat [available here](./cheatsheet.md), which explains 
+the basics of the C programming language and its compilation process on Linux.
+
+
+## Problem 1 (Mario)
+
+Let's recreate the pyramids from Super Mario in text:
+```c
+     #
+    ##
+   ###
+  ####
+ #####
+######
+```
+
+So, the program should prompt the user to input the height of the pyramid
+and then output the pyramid of the specified height:
+```c
+$ ./mario
+Height: 6
+     #
+    ##
+   ###
+  ####
+ #####
+######
+```
+
+Other examples:
+```c
+$ ./mario
+Height: 2
+ #
+##
+```
+```c
+$ ./mario
+Height: 1
+#
+```
+
+## Problem 2
+
+Create a program that takes two integer numbers as an input from the user 
+(a ≤ b) and for every number in the interval [a; b] outputs: 
+
+* the number in plain text english if it's less than 10
+* otherwise, whether it's `odd` or `even`
+
+```c
+$ ./interval
+Input a: 8
+Input b: 11
+
+eight
+nine
+even 
+odd
+```
+
+Other examples:
+```c
+$ ./interval
+Input a: 13
+Input b: 15
+
+odd
+even
+odd
+```
+```c
+$ ./interval
+Input a: 1
+Input b: 4
+
+one
+two
+three
+four
+```
+
+## Problem 3
+
+Develop a program which is going to output English text according to these rules:
+* First, all the whitespace are deleted
+* Let the length of the text taken as an input be `L`. 
+Then, output the text as a table with the number of rows and columns, where 
+`[√L] ≤ rows ≤ columns ≤ [√L] + 1` ([x] is an integer part of the number) 
+
+For example, the message `capital is an abstract parasite, an insatiable 
+vampire and zombie maker; but the living flesh it converts into dead labor 
+is ours, and the zombies it makes are us` has a length of 134 symbols without 
+the whitespace, we can output it in a table 12 x 12.
+
+```c
+capitalisan
+abstractpar
+asite,anins
+atiablevamp
+ireandzombi
+emaker;butt
+helivingfle
+shitconvert
+sintodeadla
+borisours,a
+ndthezombie
+sitmakesare
+us
+```
+
+You have to check whether `rows × columns ≥ L` and if there are several
+possible rectangles choose the one with the smaller area.
+
+Other examples:
+```c
+$ ./table
+Input your text: it is time that lived moments replace the dead memory that has stamped acquaintance with the hidden restriction that nothing can ever be experienced.
+
+Characters total: 126
+Rows: 11
+Columns: 12
+
+itistimethat
+livedmoments
+replacethede
+admemorythat
+hasstampedac
+quaintancewi
+ththehiddenr
+estrictionth
+atnothingcan
+everbeexperi
+enced.
+```
+
+## Problem 4
+
+Develop a program which, taking two integer arrays as its input will
+create a new integer array. The new array consists of the digits of the sum of the original
+two arrays' elements.
+
+So, for the example if given two arrays {23, 5, 2, 7, 87} and {4, 67, 2, 8}, 
+the new array will look like this {2, 7, 7, 2, 4, 1, 5, 8, 7}.
+
+If the array is empty, just consider the respective elements as zeros.
+Then, if given two arrays { } and {4, 67, 3, 8} then the new array will look 
+like {4, 6, 7, 3, 8}.
+
+An example usage:
+```
+$ ./arrays
+Input the length of the first array: 5
+Input the numbers: 5
+23
+5
+2
+7
+87
+
+Input the length of the second array: 5
+Input the numbers: 4
+4
+67
+2
+8
+
+The output array: 
+2 7 7 2 4 1 5 8 7
+```