1 /*
2 设计包含 min 函数的栈(栈)
3 定义栈的数据结构,要求添加一个 min 函数,能够得到栈的最小元素。
4 要求函数 min、push 以及 pop 的时间复杂度都是 O(1)。
5 */
6 #include <iostream>
7 #include <stack>
8 #include <cassert>
9
10 template<class T> class Stack
11 {
12 public:
13 void push(const T& t);
14 void pop();
15 T top() const;
16 T min() const;
17
18 private:
19 std::stack<T> m_stack, min_stack;
20 };
21
22 template<class T>
23 void Stack<T>::push(const T& t)
24 {
25 m_stack.push(t);
26 if(min_stack.empty())
27 min_stack.push(t);
28 else if(t < min_stack.top())
29 min_stack.push(t);
30 else
31 min_stack.push(min_stack.top());
32 }
33 template<class T>
34 void Stack<T>::pop()
35 {
36 assert(!m_stack.empty() && !m_stack.empty());
37 m_stack.pop();
38 min_stack.pop();
39 }
40 template<class T>
41 T Stack<T>::top() const
42 {
43 assert(!m_stack.empty());
44 return m_stack.top();
45 }
46 template<class T>
47 T Stack<T>::min() const
48 {
49 assert(!min_stack.empty());
50 return min_stack.top();
51 }
52
53 using namespace std;
54 int main(int argc, char const *argv[])
55 {
56 Stack<int> s;
57 s.push(8);
58 s.push(3);
59 s.push(7);
60 s.push(4);
61 s.push(1);
62 s.push(3);
63 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
64 s.pop();
65 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
66 s.pop();
67 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
68 s.pop();
69 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
70 s.pop();
71 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
72 s.pop();
73 cout<<"s.top = "<<s.top()<<" s.min = "<<s.min()<<endl;
74 return 0;
75 }
