vector类的简单实现
1 #include <vector>
2 #include <iostream>
3 #include <cstring>
4 #include <cassert>
5 using namespace std;
6
7 template<typename T>
8 class MyVector{
9 private:
10 const size_t WALK_LENGTH = 16;
11
12 T* _array;
13 size_t _size;
14 size_t _capacity;
15 public:
16 MyVector():_array(nullptr),_size(0),_capacity(0){}
17
18 MyVector(size_t n,T value = 0){
19 _capacity = WALK_LENGTH;
20 while(n > _capacity){
21 _capacity += WALK_LENGTH;
22 }
23 _array = new T[_capacity];
24 _size = n;
25 while(n--){
26 _array[n] = value;
27 }
28 }
29
30 MyVector(const MyVector<T>& other){
31 this->_size = other._size;
32 this->_capacity = other._size;
33 this->_array = new T[_capacity];
34 memcpy(_array,other._array,sizeof(T)*_capacity);
35 }
36
37 ~MyVector(){
38 if(this->_array){
39 delete [] this->_array;
40 }
41 }
42
43 MyVector<T>& operator=(const MyVector& other){
44 if(this == &other){
45 return *this;
46 }
47 if(this->_array){
48 delete [] _array;
49 }
50 this->_array = new T[other._capacity];
51 this->_capacity = other._capacity;
52 this->_size = other._size;
53 memcpy(this->_array,other._array,_capacity*sizeof(T));
54 return *this;
55 }
56
57 T operator[](size_t index){
58 assert(index < this->_size);
59 return _array[index];
60 }
61
62 size_t size(){
63 return this->_size;
64 }
65 size_t capacity(){
66 return this->_capacity;
67 }
68 bool isEmpty(){
69 return this->_size == 0;
70 }
71
72 void push_back(const T& t){
73 if(this->_size == this->_capacity){
74 T* tmp = this->_array;
75 this->_array = new T[_capacity+WALK_LENGTH];
76 memcpy(this->_array,tmp,this->_size*sizeof(T));
77 this->_capacity += WALK_LENGTH;
78 delete [] tmp;
79 }
80
81 this->_size += 1;
82 _array[_size -1] = t;
83 }
84
85 void insert(size_t pos,const T& t){
86 assert(pos <= _size);
87
88 if(_size == _capacity){
89 _capacity += WALK_LENGTH;
90 T* tmp = _array;
91 _array = new T[_capacity];
92 memcpy(_array,tmp,sizeof(T)*_size);
93 delete [] tmp;
94 }
95 for(size_t i = _size-1;i>=pos;i--){
96 _array[i+1] = _array[i];
97 }
98 _array[pos] = t;
99 _size += 1;
100 }
101
102 void erase(size_t pos){
103 assert(pos < _size);
104
105 for(size_t i=pos+1;i<_size;i++){
106 _array[i-1] = _array[i];
107 }
108 _size--;
109 }
110 };
111
112
113 int main(){
114 MyVector<int> v(3);
115 v.push_back(4);
116 v.push_back(10);
117 v.insert(1,100);
118 v.erase(2);
119 std::cout << v[3] << std::endl;
120 std::cout << v.capacity() << std::endl;
121 std::cout << v.size() << std::endl;
122 for(size_t i=0;i<v.size();i++){
123 std::cout << v[i] << ",";
124 }
125 std::cout << std::endl;
126 return 0;
127 }
