PPR.cpp

// Pre Placement Revision Guide!
// All the very best for placements!

#include <bits/stdc++.h>
using namespace std;

/*
        THIS RESOURCE WAS MADE FOR END MIN REVISION OF SOME INBUILT DS AND CONTAINERS THAT C++ STL
        HAS TO OFFER.
        IF THERE IS ANY BUG OR ERROR PLEASE LET ME KNOW!
*/

/*
    LIST OF CONTAINERS:

    1) sorting a vector
    2) sorting a vector in reverse order
    3) sorting a pair based upon second element of pair(in decreasing order)
    4) max-heap
    5) min-heap
    6) set(it is a kind of binary tree)
    7) multi-set
    8) map
    9) stack
    10) queue
    11) dequeue

*/
bool comp1(int &a, int &b)
{
    return a > b;
}

bool comp3(pair<int, int> &a, pair<int, int> &b)
{
    return (a.second > b.second); // sorts the vector in decreasing order acc to there second element
}

int main()
{

// 1) and 2) sorting a vector and sorting a vector in reverse order

    vector<int> vec; //vector is like an dynamic size array
    for (int i = 0; i < 5; i++)
    {
        vec.push_back(5 - i); // push_back is used to append elements at the back of vector
    }
    sort(vec.begin(), vec.end()); // sorts the vector in increasing order
    cout << vec[0] << endl;
    sort(vec.begin(), vec.end(), comp1); // sorts the vector in decreasing order
    cout << vec[0];

// 3) sorting a pair based upon second element of pair(in decreasing order)

    vector<pair<int, int>> pvec;
    pvec.push_back(make_pair(5, 6)); // make pair is used for making pair of the form of (x,y)
    pvec.push_back(make_pair(4, 5));
    pvec.push_back(make_pair(3, 5));
    pvec.push_back(make_pair(3, 6));
    pvec.push_back(make_pair(2, 6));

    sort(pvec.begin(), pvec.end(), comp3);
    for (auto x : pvec)
    {
        cout << x.first << " " << x.second << endl;
    }

// (4) max heap implimentation
    cout << "MAX HEAP \n";
    priority_queue<int> heap;
    heap.push(10); // push is used to insert elements in a heap
    heap.push(40);
    heap.push(5);
    cout << heap.top() << " "; // top is used to acess the top element
    heap.pop();                // pop is used to delete the top element
    cout << heap.top() << endl;

// (5) min heap implimentation
    cout << "MIN HEAP :\n";
    priority_queue<int, vector<int>, greater<int>> min_heap;
    min_heap.push(18);
    min_heap.push(15);
    min_heap.push(12);
    min_heap.push(10);
    min_heap.push(19);
    cout << min_heap.top() << " ";
    min_heap.pop();
    cout << min_heap.top() << endl;

// (6) set
    cout << "SET :\n";
    set<int> myset;
    myset.insert(5); //inserting the elements in set
    myset.insert(3);
    myset.insert(8);
    myset.insert(4);
    myset.insert(2);
    myset.insert(6);
    myset.insert(9);
    set<int>::iterator it = myset.find(10); // declaration of iterator for set
    if (it == myset.end())
    {
        cout << "10 is not present in myset\n";
    }
    myset.erase(8);               // for erasing an element
    cout << myset.size() << '\n'; //size of set


// (7) Multiset
    /*
        We can insert multiple elements in multiset but the same can't be done with set.
    */
    cout << "MULTISET: \n";
    multiset<int> mymultiset;
    mymultiset.insert(4);
    mymultiset.insert(3);
    mymultiset.insert(3);
    mymultiset.insert(4);
    mymultiset.insert(5);
    multiset<int>::iterator it7;
    it7 = mymultiset.find(4);
    if (it7 != mymultiset.end())
    {
        cout << "4 found in mymultiset\n";
    }
    mymultiset.erase(it7);
    cout << mymultiset.size() << "\n";

// (8) map
    cout<<"MAPS : \n";
    map<int,int> mp;
    for(int i=0;i<5;i++)
    {
        mp[i]++;
    }
    for(auto it8=mp.begin();it8!=mp.end();it8++)
    {
        cout <<it8->first<<" "<<it8->second<<endl;
    }
    // or we can directly acess an element like :
    cout <<mp[4]<<'\n';
    // map of some undeclared value will return 0, please remember.
    cout <<mp[199]<<'\n';


// (9) stacks
    cout <<"STACK : \n";
    stack<int> stk;
    stk.push(10);
    stk.push(9);
    stk.push(8);
    cout <<stk.top()<<endl;
    stk.pop();
    cout <<stk.top()<<endl;
    cout <<stk.size()<<endl;

// (10) queue

    cout <<"QUEUE : \n";
    queue<int> q;
    q.push(1);
    q.push(2);
    q.push(4);
    q.push(1);
    cout <<q.front()<<endl;
    q.pop();
    q.pop();
    cout <<q.front()<<endl;
    

// (11) deque

    cout <<"DEQUE : \n";
    deque<int> dq; //doubly ended queue
    dq.push_back(10); //appends an element at the back of dq
    cout <<dq.size()<<endl;
    dq.push_front(20); //adds element at the front of dq
    cout <<dq.size()<<endl;
    dq.pop_front(); //removes element from the front
    cout <<dq.size()<<endl;
    dq.pop_back(); // removes element from back
    cout <<dq.size()<<endl;


/******************************************************END*************************************************/

    return 0;
}