[C++][数据结构]栈的实现

 1 #pragma once
 2 #include <cstddef>
 3 #include <stdexcept>
 4 
 5 namespace jt {
 6 
 7 template <class value>
 8 class stack {
 9   template <class v>
10   friend void _stack_copy(stack<v>& dst, const stack<v>& src);
11 
12 private:
13   struct _stack_impl;
14   _stack_impl *_impl = nullptr;
15   size_t _siz;
16 
17   void _init_empty() {
18     _siz = 0;
19     if (_impl) delete _impl;
20     _impl = new _stack_impl;
21   }
22 
23   void _destory() { _siz = 0; delete _impl; }
24 
25 public:
26   stack() { _init_empty(); }
27   stack(const stack<value> &o) { _stack_copy(*this, o); }
28   ~stack() { _destory(); }
29 
30   void clear() { _init_empty(); }
31   void push(const value &val) { _impl->push(val); ++_siz; }
32   size_t size() const { return _siz; }
33 
34   value pop() {
35     if (_siz == 0)
36       throw std::out_of_range("jt::stack::pop() - Empty Stack");
37     --_siz; return _impl->pop();
38   }
39 
40   bool empty() const { return _siz == 0; }
41 
42   value top() const {
43     if (_siz == 0)
44       throw std::out_of_range("jt::stack::top() - Empty Stack");
45     return _impl->n->val;
46   }
47 };
48 
49 template <class value>
50 static void _stack_copy(stack<value> &dst, const stack<value> &src) {
51   dst._init_empty();
52   auto **dn = &dst._impl->n; // dest node
53 
54   for (auto *s = src._impl->n; s; s = s->next) {
55     *dn = new typename stack<value>::_stack_impl::node;
56     (*dn)->val = s->val;
57     (*dn)->next = nullptr;
58     dn = &(*dn)->next;
59   }
60 
61   dst._siz = src._siz;
62 }
63 
64 template <class value>
65 struct stack<value>::_stack_impl {
66   struct node {
67     value val;
68     node *next = nullptr;
69   } *n = nullptr; // head/top
70 
71   ~_stack_impl() {
72     while (n) {
73       auto *tmp = n->next;
74       delete n;
75       n = tmp;
76     }
77   }
78 
79   void push(const value& val) {
80     node *t = new node;
81     t->val = val;
82     t->next = n;
83 
84     n = t;
85   }
86 
87   value pop() {
88     value v = n->val;
89 
90     node *tmp = n->next;
91     delete n;
92     n = tmp;
93 
94     return v;
95   }
96 };
97 
98 }