C++ Data Structures Cheat Sheet
by Hackin7 via cheatography.com/71996/cs/18253/
Pointers
Storing, data type of pointers and variables must be the same
&var Returns address of memory location of variable
data_type
*pointer;
Initia๎lize. Put * in front of name
*pointer Returns value at the memory location stored by
pointer
Array variables are actually pointers to the first el ement in the array.
The amount that your pointer moves from an a rithmetic operation
*array Returns first element in array
*(array+2) Returns third element in array
โ Variables that you declare are stored in a mem ory location in your
computer
โ The address of these memory locations can be stored in pointers
โ Addresses are in hexade๎cimal
Iterators
//Append ::iterator to your data type declaration
to create an iterator of
that data type
vector๎<in๎t>:๎:it๎erator it; // declares an iterator
of vector๎<in๎t>
// loops from the start to end of vi
for(ve๎cto๎r<i๎nt>๎::i๎terator it = vi.beg๎in(); it !=
vi.end(); it++)
๎ ๎ ๎ cout << *it << " "; // outputs 1 2 3 4
deque<๎int> d;
deque<๎int๎>::๎ite๎rator it;
it = d.begin(); //Points to first element
it++; // Points to next element
it = d.end(); // Points to Last element
it--; // Points to previous element
cout << *it; // outputs the element it is pointing
Iterators are essent๎ially pointers to an STL data s tructure
Maps
map<string, int> M;
M[โhelloโ] = 2;
M[โasdโ] = 986;
M.coun๎t(โ๎asdโ); // returns 1
M.coun๎t(โ๎doe๎snt๎_ex๎istโ); // returns 0
M.size();
// Check for the existence of some key in the map -
O(log N)
it = M.find๎(โa๎sdโ); //returns the iterator to
โasdโ
it = M.uppe๎r_b๎oun๎d("a๎aa");
it = M.lowe๎r_b๎oun๎d("a๎aa");
if (it == M.end())
๎ ๎ ๎ cout << "Does not exist๎\n";
//Iter๎ation
for (auto it = mp.beg๎in(); it != mp.end(); ++it) {
๎ ๎ ๎ cout << it.first << โ, โ << it.second << โ\nโ;
}
A data structure that takes in any data[key]
Gives you the associated value stored through O (log N) magic
Best used when you need to lookup certain valu es in O(log N) time
that are associated with other values
Queue
queue<int> q;
q.push(5); // Inserts/ Enqueue element at the back
of the queue
q.front(); // Returns element atb the front of the
queue
q.pop // Removes (Dequeues) element from the front
of the queue
q.empty(); // Returns boolean value of whether
queue is empty
First In First Out data structure where elements can only be added to
the back and accessed at the front
By Hackin7
cheatography.com/hackin7/
Published 12th December, 2018.
Last updated 27th December, 2019.
Page 1 of 5.
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