C++ crash course

Class 10 practice problems

Pointers

The following function is trying to swap the contents of two variables. Why isn’t it working?

} void swap(int &a, int b) { int tmp = a; a = b; b = tmp;

Strings

• Write a function which, given a char array and two ints, will return a string * which holds the section between the two ints. Return the null pointer if it’s not possible.

string *substr(char arr[], int start, int stop);

Dynamic Memory Allocation

• The below is bad practice. Why is that?

int *p = new int(5); int j = 7; p = &j;

Pointers

• This won’t compile. Why?

double a = 10; int *aptr = &a;

Pointers

• What is “this”, and what is its use?

Data Types

• How is initializing a vector of ints different from initializing a single int?

Data Types

• Write the following in decimal.

101001 2 0456 0x21

Files and Unix

• What’s the difference between > and < on the Unix command line?

What’s the output?

int size = 3; int arr[12] = {7, 2, 4}; char name[12] = “Jeff Jones”; int *iptr; char *cptr; iptr = arr; cout << iptr[1] << “ and “ << *iptr << endl; cptr = &name[5]; cout << cptr << endl; cout << *(cptr + 3) << “ and “ << *(cptr-4) << endl; cptr ++; cout << name[3] << “ and “ << cptr[3] << endl;

Operators

• What do all of the following do?

*itr++; *++itr; (*itr)++;

}

What does this output?

void funct(int a); int main() { int a = 5, *b = &a, c[] = {10, 21, 12}; int *d, *e, f; cout << *b << “ “ << *c + 1 << endl; e = b; b = new int; d = new int; *d = 7; *b = 9; *e = 11; cout << *e << *d << a; funct(a); e = b; free(b); cout << *e << f << a; return 0;

Scope

• What’s the scope operator (::) doing in these instances?

std::cout int Animal_type::avg_age() const What can you do to avoid using the scope operator repeatedly?

Overloading Operators

• What’s the function prototype to overload the output operator?

– return type – function name – parameter list

const

• What is the purpose of the “const” keyword?

• const gets a little tricky with pointers. Give an example.

Loops

• Write a function to sum even numbers from int a to int b, and return the result.

Reserved Words

• What are reserved words? Give 3 examples.

Functions

• What’s the difference between int a, int &a, and int *a in a function parameter list?

?

• What are these called? What do they do?

#include #define #ifndef #endif

Operators

• What is precedence? What is associativity?

• • Is assignment left or right associative?

Is arithmetic left or right associative?

Sorting

• Sort these using insertion sort, and show all the steps.

5 4 15 99 46 82 93 54 71 26 12

Sorting

• Write an insertion sort on a vector of int *.

Classes

• What’s a constructor? How do you identify one?

• Write a default constructor for this class: class Mystery { int a; bool b; string s; };

Classes

• What is the difference between public, private and friend?

Data Types

• What’s the difference between a literal and a constant?