1 #pragma warning(disable:4996)
2 #include<iostream>
3 #include<string>
4 #include<vector>
5 #include<algorithm>
6 #include<cstdio>
7 #include<complex>
8 #include<new>
9 #include<memory>
10 #include<exception>
11 #include<cstdlib>
12 #include<iterator>
13 #include<initializer_list>
14 using namespace std;
15 //template<typename t> class alloc
16 //{public:
17 // alloc():a(),s(){ //成员变量默认初始化
18 // }
19 // t* allocate(size_t n){
20 // return a.allocate(n);
21 // }
22 ////变长模板参数，allocator的第二个参数是变长的，要调用它，外层的construct也要有变长参数
23 //template<typename...Args> void construct(t* p, const Args&...rest){
24 // a.construct(p,rest... );
25 // }
26 // void deallocate(t* p, size_t n)
27 // {
28 // a.deallocate(p, n);
29 // }
30 // void destory(t* p)
31 // {
32 // a.destory(p);
33 // }
34 //
35 //
36 //private:
37 // allocator<t> a;
38 // string s;
39 //
40 //};
41 //vector为空，capacity=0,否则预分配空间为16，当空间不足时，扩大两倍增长，
42 template<typename T, class Allocator = std::allocator<T> >
43 class Vector{
44 private:
45 T* start;
46 T* finish;
47 T* end_of_storage;
48 size_t length;
49 size_t capacity;
50 public:
51 typedef T* iterator;
52 typedef const T* const_iterator;
53 Vector():start(NULL),finish(0){
54 end_of_storage = NULL;
55 length = 0;
56 capacity = 0;
57 }
58 Vector(const std::initializer_list<T> &lst)
59 {
60 for (auto it = lst.begin(); it != lst.end();it++)
61 {
62 this->push_back(*it);
63 }
64
65 }
66 Vector(size_t n, const T&value = T()){
67 Allocator a;
68 T*p = NULL;
69 if (n <= 16){ p = a.allocate(16);
70 capacity = 16;
71 }
72 else {
73 p = a.allocate(static_cast<int>(1.5 * n));
74 capacity = static_cast<size_t>(1.5*n);
75 }
76 start = p;
77 finish=uninitialized_fill_n(p, n, value);
78 if (n <= 16) end_of_storage = start + 15;
79 else end_of_storage = p + static_cast<int>(1.5*n)-1;
80 length = n;
81 }
82 /*Vector(size_t n, const T&value){ Vector(n, value); }*/
83 Vector(const Vector& rhs){
84 capacity = rhs.capacity;
85 length = rhs.length;
86 Allocator a;
87 start=a.allocate(capacity);
88 end_of_storage = start + capacity - 1;
89 finish = start + length ;
90
91 for (T* p = start,*q = rhs.start; p != finish; p++, q++){
92 a.construct(p, *q);
93 }
94 }
95 void push_back(const T& value){
96 if (capacity == 0){ //为空容器时需要申请新空间
97 Allocator a;
98 start = a.allocate(16);
99 a.construct(start, value);
100 finish = start + 1;
101 end_of_storage = start + 15;
102 length = 1;
103 capacity = 16;
104 }
105 else if (length < capacity){
106 Allocator a;
107 a.construct(finish++, value);
108 length += 1;
109 }
110 else { //空间不足时1.5倍扩大空间
111 Allocator a;
112 auto old_capacity = capacity;
113 auto new_start = a.allocate(static_cast<size_t>(1.5*capacity));
114 auto new_finish = uninitialized_copy(this->begin(), this->begin()+length, new_start); //没有使用迭代器形式
115 new_finish = uninitialized_fill_n(new_finish, 1, value);
116 //释放掉旧空间
117 capacity = static_cast<size_t>(1.5*capacity);
118 length += 1;
119
120 auto temp = start;
121 while (temp != finish)
122 {
123 a.destroy(temp++);
124 }
125 a.deallocate(start, old_capacity);
126 start = new_start;
127 finish = new_finish;
128 end_of_storage = start + capacity - 1;
129 }
130 }
131 void pop_back(){//弹出的意义是不在含有该对象
132 Allocator a;
133 a.destroy(--finish); //finish指向尾后位置，自减后销毁了对象，不存在了
134 length -= 1;
135
136 }
137 iterator insert(const_iterator position, const T&value);
138 T& operator[](size_t n){return *(start + n); } //如果index out of bound or Vector为空 ,让用户自己去处理
139 const T& operator[](size_t n)const { return *(start + n); }
140 T& front(){ return *start; }
141 const T&front()const{ return *start; }
142 T& back(){ return *(finish-1); }
143 const T&back()const{ return *(finish - 1); }
144 size_t size(){ return length; }
145 size_t volume(){ return capacity; }
146 iterator begin(){ return start; }
147 const_iterator cbegin()const { return start; }
148 iterator end(){ return finish; }
149 const_iterator cend(){ return finish; }
150 Vector& operator=(const Vector&rhs){
151 if (this->start ==rhs.start) return *this; //两个相等，两个相同
152 //释放掉原有的内存空间，allocator分配的空间如果不deallocate,会造成内存泄漏
153 auto old_start = this->start;
154 auto old_finish = this->finish;
155 size_t old_capacity = this->capacity;
156 capacity = rhs.capacity;
157 length = rhs.length;
158 Allocator a;
159 start = a.allocate(capacity);
160 end_of_storage = start + capacity - 1;
161 finish = start + length;
162
163 for (T* p = start, *q = rhs.start; p != finish; p++, q++){
164 a.construct(p, *q);
165 }
166 Allocator b;//是需要重新创建b，还是用前面的a就可以完成下面的动作
167 T* p = old_start;
168 while (p!=old_finish)
169 {
170 b.destroy(p++);
171 }
172 b.deallocate(old_start, old_capacity);
173 return *this;
174
175 };
176 ~Vector(){
177 Allocator a;
178 T* p = start;
179 while (p!= finish)
180 {
181 a.destroy(p++);
182 }
183 a.deallocate(start, capacity);
184 start = finish = end_of_storage = NULL; //是否多余语句
185 cout << " dectr completed";
186 }
187
188 };
189 template<typename T>
190 class demo{
191 public:
192 demo():d(){}
193 T size();
194 private:
195 T d;
196 };
197 class foo{
198 public:
199 foo() :a(5), s("dka"){}
200 private:
201 int a; string s;
202
203 };
204
205 int main()
206 {
207 Vector<string> v1;
208 cout << v1.volume() << " " << v1.size() << "\n";
209 Vector<string> v2(10);//10个空串，调用了string的default ctr
210 cout << v2.size() << " " << v2.volume() << endl;
211 cout << "the first item of v2: " << v2[0] << " or " << v2.front() << endl;
212 //Vector<string> v3(10, ‘c‘); no instance of parameters (int,char)
213 Vector<string> v4(10, "c");
214 Vector<string> v5(v4);
215 cout << v5.back() << " " << v5.size() << v5.volume() << endl;
216 v5 = v1;
217 for (auto it = v5.begin(); it!= v5.end();it++)
218 {
219 cout << *it;
220 }
221 /*cout << v5[0] << endl;*/
222
223 Vector<string> v6(v1); //用空vector初始化另一个vector ;这两个vector都应该表现正常
224 for (auto it = v6.cbegin(); it != v6.cend();it++)
225 {
226 cout << *it << endl;
227 }
228 v1 = v4;//v1原本为空，用含10个元素的v4赋值，并用push_back添加尾元素
229 for (auto x : v1) cout << x << endl;
230 v1.push_back("hdwa");
231 cout << v1.size() << v1[10] << endl;
232 v1.pop_back();
233 cout << v1.back() << endl;
234 string s;
235 Vector<int> iv(10);
236 for (auto y:iv)
237 {
238 printf("%d", y);
239 }
240 Vector<string> v7={ "dak", "dj" };
241 cout << v7.volume() << " " << v7.size() << v7[0] << " " << v7[1] << endl;
242
243
244 }
时间： 2024-12-12 09:44:38