3.4 Queue via Stacks

class Queue {
public:
stack<int> stkIn;
stack<int> stkOut;
// Push element x to the back of queue.
void push(int x) {
stkIn.push(x);
}

// Removes the element from in front of queue.
void pop(void) {
peek();
stkOut.pop();
}

// Get the front element.
int peek(void) {
if(stkOut.empty()){
while(stkIn.size()){
stkOut.push(stkIn.top());
stkIn.pop();
}
}
return stkOut.top();
}

// Return whether the queue is empty.
bool empty(void) {
return (stkOut.empty() && stkIn.empty());
}
};