Amaraj's Guide To Technical Interviews

General Advice

• Talk through the problem solving process
• First consider the algorithm that you would want to implement
• Think about the problem for a while and then code it out, so many errors aren't made
• After writing the code, immediately test it by running through an example case
• Check code for all boundary conditions and special cases
• Almost all coding questions have short answers

Object Oriented Programming

Recursion

• A function is recursive if it calls itself
• A recursive problem will have at least one "trivial" base or "stopping" case and all other cases can be solved by first solving one or more smaller cases, and then combining the solutions
• With tail recursion there is no pending computation at each recursive step, so the activation record on the stack can be reused
• Writing a tail recursive function often requires a helper function that is passed "extra" arguments that keep track of the current "state" of the computation

Function Pointers

• int (*foo)(int, int) means foo is a pointer to a function that takes in two ints as arguments and returns an int
• Once foo has been declared, any defined function that matches the type signature can be assigned to it foo = min and can then be called by foo(3,5)

Arrays

• A fixed-size, zero-indexed, homogeneous aggregate type
• int array[4] to initialize and int array[4] = {1,2,3,4} would be static initialization
• Arrays can be passed into functions in this manner: int sum(int a[], unsigned int size) so that the function call would be sum(array, 4)
• Arrays are passed by reference not value
• C-style string is an array of zero or more chars followed by a null character, which acts as the sentinel and signals the end of an aggregate

Pointers

• A 'pointer-to-T' is a variable that can hold the address of some other object of type T
• int *bar means bar is a pointer to an int
• Bar can be assigned an address of an int: int *bar; int foo; bar = &foo; where the ampersand means "address-of"
• *bar = 2 means change the value of the object to which bar points to 2, where the * is called the dereference operator
• Pointers are used because they provide a convenient mechanism to work with arrays (pointer arithmetic) and allow structures to be created whose size is not known in advance

Array Traversal

• array[3] == *(array + 3)
• for(int *i = array; i < array + SIZE; ++i)
• In *p++ the ++ "binds tighter" that * so it is saying "dereference the pointer given its current value, and then increment it after you are done"

Const Keyword

• const is a type qualifier - something that modifies a type, that means that you cannot change this value once it is initialized
• const T *p; - "T" (the pointed-to object) cannot be changed
• T *const p - "p" (the pointer) cannot be changed
• Allows any mistakes to be caught by the compiler
• Use const for things that are passed by reference, but won't be changed

Structs & Classes

• Structs are passed by value and therefore should be passed by reference or use pointers
• t->a is way to access data inside pointer-to-struct
• A class contains member data and member functions
• By default every member of a class is private, so get and set functions are sometimes used to access and alter the values of member variables

Constructors

• A member function with the same name as the class that is used to initialize member variables
• Runs automatically when a new object is created
• Default Constructor takes no input: Rectangle() {short = 0, long = 0;}
• Function Overloading: two different functions with the same name, but different prototypes as in to overload the default constructor,

Rectangle(int short_in, int long_in) { short = short_in; long = long_in}

Data Structures

Linked Lists

Overview

• Consists of a number of data elements in which each data element has a next pointer or next reference
• The last element in the list has a null pointer
• A pointer to the first element, or head of the list is needed, and is the element that is typically passed into functions
• The head pointer must be updated when a new element is added to the list or when the existing first element is removed
• When traversing a linked list, always check for the end of the list to avoid seg faults
• Insertion and deletion require a pointer or reference to the element immediately preceding the deletion or insertion location

Unix Utilities