Container adapters

C++ Algorithms

Mohammed SikanderTeam LeadCranes [email protected]

Mohammed Sikander www.cranessoftware.com

Container adapters, are interfaces created by limiting functionality in a pre-existing container and providing a different set of functionality. When you declare the container adapters, you have an option of specifying which sequence containers form the underlying container.

These are:

Stack

Queue

priority_queue

http://www.cranessoftware.com/


The stack class is a container adapter that gives the programmer the functionality of a stack (LIFO) data structure.

The class template acts as a wrapper to the underlying container - only a specific set of functions is provided.

The stack pushes and pops the element from the back of the underlying container, known as the top of the stack.



Function Name Prototype Description

push void push (const value_type& val); Insert element

pop void pop(); Remove top element

top value_type& top(); Returns a reference to the top element in the stack.

empty bool empty() const; Test whether container is empty



#include <stack>

int main( ) {

stack<int> s;

int ele , ch;

for(;;) {

cout <<"1. Insert 2. Delete 3. Terminate \n";

cin >> ch;

switch(ch)

{case 1 : cout <<"Enter the element to insert : ";

cin >> ele;

s.push(ele);

break;

case 2 : if(s.empty() == false) {

cout <<"The deleted element is " << s.top()<<endl;

s.pop();

}

break;

default : return 0;

}

}

}



#include <stack>int main( ){

string str;cout << “Enter the string : “;cin >> str;stack <char> stk;for(int i = 0 ; i < str.length() ; i++)

stk.push(str[i]);

cout <<“The reverse string is \n”;while(stk.empty() == false ){

cout <<stk.top() ;stk.pop();

}}



Given a sequence consisting of parentheses, determine whether the expression is balanced. A sequence of parentheses is balanced if every open parentheses can be paired uniquely with a closed parentheses that occurs after the former. Also, the interval between them must be balanced. You will be given three types of parentheses: (, {, and [.

{[()]} {[(])} {{[[(())]]}}



bool checkparenthesis(string s) {stack <char> stk;for(int i = 0 ; i < s.length() ; i++) {

if(s[i] == '[' || s[i] == '(' || s[i] == '{')stk.push(s[i]);

else {if(stk.empty() == true)

return false;if(s[i] == ']' && stk.top() == '[‘) {

stk.pop(); continue;}else if(s[i] == '}' && stk.top() == '{‘) {

stk.pop(); continue;}if(s[i] == ')' && stk.top() == '(‘) {

stk.pop(); continue; }

return false; }

}return stk.empty() ;}



The queue class is a container adapter that gives the programmer the functionality of a queue (FIFO) data structure.

The queue pushes element from back (rear) and pops the element from front of the underlying container.





pop void pop(); Remove next element

front value_type& front(); Returns a reference to the first element in the queue.

back value_type& back(); Returns a reference to the last element in the queue.



http://www.cplusplus.com/queue

http://www.cplusplus.com/queue


#include <queue>

int main( ) {

queue<int> q;

int ele , ch;

for(;;) {

cout <<"1. Insert 2. Delete 3. Terminate \n";

cin >> ch;

switch(ch)

{

case 1 : cout <<"Enter the element to insert : ";

cin >> ele;

q.push(ele);

break;

case 2 : if(q.empty() == false)

{

cout <<"The deleted element is " << q.front()<<endl;

q.pop();

}

break;

default : return 0;

}

}

}



A priority_queue is a container providing sorted-order access to elements.

You can insert elements in any order, and then retrieve the "lowest" of these values at any time.

Priority queues in C++ STL use a heap structure internally.





pop void pop(); Remove next element

top value_type& top(); Returns a reference to the top element in the priority queue.




#include <queue>int main( ) {

priority_queue <int> pq;int ele , ch;for(;;) {

cout <<"1. Insert 2. Delete 3. Terminate \n";cin >> ch;switch(ch){case 1 : cout <<"Enter the element to insert : ";

cin >> ele;pq.push(ele);break;

case 2 : if(pq.empty() == false) {cout <<"The deleted element is " << pq.top()<<endl;pq.pop();

} break;default : return 0;}

}}



#include <queue>int main( ){

priority_queue <int> pq;int ele;

for(int i = 0 ; i < 5 ; i++){

cin >> ele;pq.push(ele);

}

while(pq.empty() == false){

cout << pq.top() <<" ";pq.pop( );

}}

#include <queue>int main( ){priority_queue <int , vector<int> , greater<int>> pq;

int ele;

for(int i = 0 ; i < 5 ; i++){


}

while(pq.empty() == false){

cout << pq.top() <<" ";pq.pop( );

}}


http://en.cppreference.com/w/cpp/utility/functional/greater


Jesse loves cookies. He wants the sweetness of all his cookies to be greater than value K. To do this, Jesse repeatedly mixes two cookies with the least sweetness. He creates a special combined cookie with:

sweetness =(1×=(1× Least sweet cookie + 2× 2nd least sweet cookie). He repeats this procedure until all the cookies in his collection have a

sweetness ≥K.You are given Jesse's cookies. Print the number of operations required to give the cookies a sweetness ≥K. Print −1 if this isn't possible.

Input Format The first line consists of integers N, the number of cookies and K, the minimum

required sweetness, separated by a space.The next line contains N integers describing the array A where Ai is the sweetness of the ith cookie in Jesse's collection.

Output Format Output the number of operations that are needed to increase the cookie's

sweetness ≥K≥K.Output −1−1 if this isn't possible.



Sample Input6 7 1 2 3 9 10 12

Sample Output2

Explanation Combine the first two cookies to create a cookie

with sweetness =1×1+2×2 = 5After this operation, the cookies are 3,5,9,10,12.Then, combine the cookies with sweetness 3 and sweetness 5, to create a cookie with resulting sweetness =1×3+2×5= 13Now, the cookies are 9,10,12,13.All the cookies have a sweetness ≥7.

Thus, 2 operations are required to increase the sweetness.



int main() {int n , k , ele ;

priority_queue<int , std::vector<int>, std::greater<int>> pq;

cin >> n >> k;for(int i = 0 ; i < n ; i++){


} int count = 0;while(pq.top() < k){

count++;int x = pq.top();pq.pop();if(pq.empty() == true){

cout << -1 << endl;return 0;

}

int y = pq.top();pq.pop();

int res = x * 1 + y * 2;pq.push(res);

} // End of Whilecout << count << endl;return 0;

}


Container adapters

Software

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