代码例如以下：
PS：做了一些測试，眼下没问题。有问题请指正。
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template
class myQueue
{
private:
stack push_stack;
stack pop_stack;
public:
myQueue(){}
~myQueue(){}
bool empty() const{return push_stack.empty() && pop_stack.empty();}
void push(const T &x);
void pop();
T front(); //front is not a const function !!!
};
template
void myQueue::push(const T& x)
{
push_stack.push(x);
}
template
void myQueue::pop()
{
if(empty()) throw runtime_error("empty queue!!!");
if(pop_stack.empty())
{
while(!push_stack.empty())
{
T x = push_stack.top();
push_stack.pop();
if(push_stack.empty())
return;
pop_stack.push(x);
}
}
else
{
pop_stack.pop();
}
}
template
T myQueue::front()
{
if(empty()) throw runtime_error("empty queue!!!");
if(pop_stack.empty())
{
while(!push_stack.empty())
{
T x = push_stack.top();
push_stack.pop();
pop_stack.push(x);
}
}
return pop_stack.top();
}
template
class MyStack
{
private:
queue queue1;
queue queue2;
public:
MyStack(){}
~MyStack(){}
bool empty() const {return queue1.empty() && queue2.empty();}
void push(const T & x);
void pop();
T top() ;
};
template
void MyStack::push(const T &x)
{
//if both empty, both ok
if(queue1.empty()) queue2.push(x);
else queue1.push(x);
}
template
void MyStack::pop()
{
if(empty()) throw runtime_error("empty stack!!!");
if(queue1.empty()) queue1.swap(queue2);
assert(!queue1.empty()&&queue2.empty());
while(!queue1.empty())
{
T x = queue1.front();
queue1.pop();
if(queue1.empty())
return;
queue2.push(x);
}
}
template
T MyStack::top()
{
if(empty()) throw runtime_error("empty stack!!!");
if(queue1.empty()) queue1.swap(queue2);
assert(!queue1.empty()&&queue2.empty());
T x;
while(!queue1.empty())
{
x = queue1.front();
queue2.push(x);
queue1.pop();
}
return x;
}