vector官网链接:传送门
一、构造函数
| 构造函数 | 含义 |
| vector (const allocator_type& alloc = allocator_type()); | 无参构造 |
| vector（size_type n, const value_type& val = value_type()） | 初始化为n个val |
| vector (InputIterator first, InputIterator last,const allocator_type& alloc = allocator_type()) | 迭代器区间初始化 |
| vector (const vector& x); | 拷贝构造 |
(1)无参构造
默认什么元素也没有.
有效元素个数:size=0
容量:capacity=0;
//无参构造 vector<int> v1; //auto it1 = v1.begin();//可以使用auto自动推导类型 vector<int>::iterator it1 = v1.begin(); while (it1 != v1.end()) { cout << *it1 << " "; it1 ++ ; } cout << "v1.size=" << v1.size() << endl; cout << "v1.capacity=" << v1.capacity() << endl; cout << endl;
运行结果:
v1.size=0 v1.capacity=0
(2)初始化为n个值
用n个val去初始化vector;
//初始化为n个值 vector<int> v2(4,0); //auto it2 = v2.begin(); vector<int>::iterator it2 = v2.begin(); while (it2 != v2.end()) { cout << *it2 << " "; it2++; } cout << endl;
运行结果:
0 0 0 0
(3) 迭代器区间初始化
用一个迭代器区间进行初始化,这里采用数组的头和尾作为迭代器区间.
//迭代器区间初始化 int a3[10] = { 1,3,4,5,6,7,8,98,100,11 }; vector<int> v3(a3, a3 + 10);//注意这里给的是+10,因为迭代器的end是指向最后一个有效元素的下一个位置,左闭右开 auto it3 = v3.begin(); while (it3 != v3.end()) { cout << *it3 << " "; it3++; } cout << endl;
运行结果:
1 3 4 5 6 7 8 98 100 11
(4)拷贝构造
//拷贝构造 vector<int> v4(v3);//v3就是上面的迭代器区间初始化好的v3 auto it4 = v4.begin(); while (it4 != v4.end()) { cout << *it4 << " "; it4++; } cout << endl;
运行结果:
1 3 4 5 6 7 8 98 100 11
二、容量操作
(1) 一览表
| 接口 | 说明 |
| size() | 有效数据的个数 |
| resize() | 改变有效数据的个数 |
| capacity() | 容量大小 |
| empty() | 判空 |
| reserve() | 改变容量大小 |
(2) 代码演示
void test2() { int a1[10] = { 1,3,4,5,6,7,8,98,100,11 }; vector<int> v1(a1, a1 + 10); cout << "v1.size()=" << v1.size() << endl;//显示有效数据的个数 cout << "v1.capacity()=" << v1.capacity() << endl;//显示容量的大小 cout << "v1.empty()=" << v1.empty() << endl;//判断容器是否为NULL cout << endl; v1.resize(5);//改变有效数据的个数 cout << "v1.size()=" << v1.size() << endl; cout << "v1.capacity()=" << v1.capacity() << endl; vector<int>::iterator it1 = v1.begin(); while (it1 != v1.end()) { cout << *it1 << " "; it1++; } cout << endl; v1.resize(15,66); cout << "v1.size()=" << v1.size() << endl; cout << "v1.capacity()=" << v1.capacity() << endl; cout << endl; it1 = v1.begin(); while (it1 != v1.end()) { cout << *it1 << " "; it1++; } cout << endl; v1.reserve(10);//改变容量的大小. cout << "v1.capacity()=" << v1.capacity() << endl; v1.reserve(50); cout << "v1.capacity()=" << v1.capacity() << endl; }
运行结果:
三、修改与访问
| 接口 | 说明 |
| assign() | 将新内容覆盖给容器，替换其当前内容，并相应地修改其大小。 |
| push_back() | 尾插 |
| pop_back() | 尾删 |
| insert() | 指定位置pos之前插入 |
| erase() | 删除指定位置pos的值 |
| swap() | 交换两个容器 |
operator[ ]() |
下标访问运算符重载 |
(1) push_back && pop_back
尾插和尾删相信大家已经比较熟悉了.
assign()
assign函数需要注意.
void assign (size_type n, const value_type& val);
如果n
如果n>size,则先扩容,再将n个val值存入.
//push_back &&pop_back int a1[5] = { 1,2,3,4,5 }; vector<int> v1(a1, a1 + 5); for (auto itt : v1){ //1 2 3 4 5 cout << itt << " "; } cout << endl; //尾插 v1.push_back(6); v1.push_back(7); for (auto itt : v1){ //1 2 3 4 5 6 7 cout << itt << " "; } cout << endl; //尾删 v1.pop_back(); for (auto itt : v1){ //1 2 3 4 5 6 cout << itt<<" "; } cout << endl; //将新内容覆盖给容器，替换其当前内容，并相应地修改其大小 v1.assign(5, 2); for (auto itt : v1){ //2 2 2 2 2 cout << itt << " "; } cout << endl << v1.size() << " " << v1.capacity() << endl;//5 7 cout << endl;
运行结果:
1 2 3 4 5 1 2 3 4 5 6 7 1 2 3 4 5 6 2 2 2 2 2 5 7
(2) insert()
指定位置pos之前插入.
代码演示:
int a1[5] = { 1,2,3,4,5 }; vector<int> v1(a1, a1 + 5); for (auto itt : v1){ cout << itt << " "; } cout << endl; //iterator insert(iterator position, const value_type & val); v1.insert(v1.begin() + 2, 66);//在第三个位置的前面插入数据. for (auto itt : v1) { cout << itt<<" "; } cout << endl; //void insert(iterator position, size_type n, const value_type & val); v1.insert(v1.begin() + 5, 5, -1);//在第六个位置的前面插入5个-1. for (auto itt : v1) { cout << itt << " "; } cout << endl; int a2[5] = { 1,2,3,4,5 }; int a3[5] = { 6,7,8,9,10 }; vector<int> v2(a2, a2 + 5); for (auto itt : v2) { cout << itt << " "; } cout << endl; //void insert (iterator position, InputIterator first, InputIterator last); v2.insert(v2.begin()+5,a3 ,a3 + 5); for (auto itt : v2) { cout << itt << " "; } cout << endl;
运行结果:
(3) erase()函数
删除指定位置pos的值
//erase int a4[10] = { 1,2,3,4,5,6,7,8,9,10 }; vector<int> v4(a4, a4 + 10); for (auto itt : v4) { cout << itt << " "; } cout << endl; //iterator erase (iterator position); v4.erase(v4.begin() + 1); for (auto itt : v4) { cout << itt << " "; } cout << endl; //iterator erase (iterator first, iterator last); v4.erase(v4.begin()+4, v4.begin() + 9); for (auto itt : v4) { cout << itt << " "; } cout << endl;
运行结果:
(4) swap()
用于交换两个容器,注意观察交换后容量的变化.
//swap //void swap(vector & x); int a5[10] = { 1,2,3,4,5,6,7,8,9,10 }; vector<int> v5(a5, a5 + 10); int a6[10] = { 2,4,6,8,10 }; vector<int> v6(a6, a6+5); cout << "v5="; for (auto itt : v5){ cout << itt << " "; } cout << endl; cout << "v6="; for (auto itt : v6){ cout << itt << " "; } cout << endl; swap(v5, v6); cout << endl; cout << "v5="; for (auto itt : v5){ cout << itt << " "; } cout << endl; cout << "v6="; for (auto itt : v6){ cout << itt << " "; } cout << endl; cout << "v5.capacity()" << v5.capacity(); cout << endl; cout << "v6.capacity()" << v6.capacity(); cout << endl;
运行结果:
(5) []运算符重载
可以像数组一样通过下标直接访问.
//[] int a7[10] = { 1,2,3,4,5,6,7,8,9,10 }; vector<int> v7(a5, a5 + 10); cout << "v7="; for (int i = 0; i < 10; i++) { cout << v7[i] << " "; }
v7=1 2 3 4 5 6 7 8 9 10
vector的使用就分享到这里了.下一期vector模拟实现见.
