practice problems

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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.
1010012
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?

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