C++ crash course
Class 10practice 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.
1010012
04560x21
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?