Implement Queue using Stacks

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Implement the following operations of a queue using stacks.

  • push(x) -- Push element x to the back of queue.
  • pop() -- Removes the element from in front of queue.
  • peek() -- Get the front element.
  • empty() -- Return whether the queue is empty.
Notes:
  • You must use only standard operations of a stack -- which means only push to top, peek/pop from top, size, and is empty operations are valid.
  • Depending on your language, stack may not be supported natively. You may simulate a stack by using a list or deque (double-ended queue), as long as you use only standard operations of a stack.
  • You may assume that all operations are valid (for example, no pop or peek operations will be called on an empty queue).


class Queue {public:    stack<int> stack1;    stack<int> stack2;    // Push element x to the back of queue.    void push(int x) {        stack1.push(x);            }    // Removes the element from in front of queue.    void pop(void) {        if(stack2.empty()){            while(!stack1.empty()){                stack2.push(stack1.top());                stack1.pop();            }        }        stack2.pop();    }    // Get the front element.    int peek(void) {        if(stack2.empty()){            while(!stack1.empty()){                stack2.push(stack1.top());                stack1.pop();            }        }        return stack2.top();    }    // Return whether the queue is empty.    bool empty(void) {        if(stack1.empty() && stack2.empty()){            return true;        }else{            return false;        }    }};


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