Queue - C P P

• Theory
• STL Commands for Queue
• STL Commands for Doubly Ended Queue

Theory

• FIFO (First In First Out)
• Time complexity of all operations is generally O(1)
• Enqueue => Push
• Dequeue => Pop
• Other Types
  • Circular Queue
  • Input Restricted Queue
    • Pop operation from both sides
  • Output Restricted Queue
    • Push operation from both sides
  • Doubly Ended Queue
    • Push and Pop operation from both sides

STL Commands for Queue

• #include <queue> => Header to include
• queue<dataType> var => Initialize queue
• var.push(val) => Insert value at front
• var.pop() => Returns and removes the value from front
• var.empty() => Returns boolean value true if queue is empty
• var.size() => Returns the size of queue
• var.back() => Returns last element
• var.front() => Returns first element

STL Commands for Doubly Ended Queue

• #include <deque> => Header to include
• deque<dataType> var => Initialize a deque
• var.push_front(value) => Insert element in the front
• var.push_back(value) => Insert element in the back
• var.pop_front() => Remove element from the front
• var.pop_back() => Remove element from the back
• var.at(N) => Returns element at nth index
• var.front() => Returns element at the first position
• var.back() => Returns element at the last position
• var.empty() => Returns boolean value true if deque is empty
• var.size() => Returns size of deque
• var.empty(n1, n2) => Removes element form n1 position to n2
• var.begin() => Returns an iterator pointing to the first element
• var.end() => Returns an iterator pointing to the theoretical element that follows the last element