vector学习记录

 

#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
using namespace std;

int main() {
//创建
/*
    //方法1
    vector<char> v1(20, 'a'); //(元素个数 = 0， 默认值 = 0)
    cout << "record的大小为:" << v1.size() << endl;
    cout << "record的容量为" << v1.capacity() << endl;
    for (int i = 0; i < v1.size(); i++)
        cout << v1[i] << " ";
    cout << endl;
    //方法2
    vector<char> v2{ 'a', 'b', 'c' };
    cout << "v2的大小为:" << v2.size() << endl;
    cout << "v2的容量为" << v2.capacity() << endl;
    for (int i = 0; i < v2.size(); i++)
        cout << v2[i] << " ";
    cout << endl;
*/
//容量和大小
/*
    vector<char> v(10, 'a');
    cout << "容器的元素为:";
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    cout << "容器的容量为:" << v.capacity() << endl;
    cout << "容器的大小为:" << v.size() << endl;
    v.resize(5);
    v.reserve(12);
    cout << "容器大小和容量重定义后" << endl;
    cout << "容器的元素为:";
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    cout << "容器的容量为:" << v.capacity() << endl;
    cout << "容器的大小为:" << v.size() << endl;
*/
//访问
/*
    vector<int> v{ 1, 2 };
    //cout << v[100] ;//（没有安全检查)
    //cout<< v.at(100);//有安全检查
    cout << "第一个元素为:" << v.front() << endl;  //front()返回第一个元素的引用
    cout << "最后一个元素为:" << v.back() << endl;//back()返回最后一个元素的引用
    auto a = v.data();   //返回vector中动态数组的引用
    for (int i = 0; i < 2; i++)
        cout << a[i] << " ";
*/
//迭代器
/*
    vector<int> v{ 0, 1, 2, 3, 4, 5};
    v.reserve(19);
    //正向迭代器
    cout << "使用正向迭代器" << endl;
    for (vector<int>::iterator i = v.begin(); i != v.end(); ++i) {
        cout << *i << " ";
        *i *= 2;
    }
    cout << endl;
    //反向迭代器
    cout << "使用反向迭代器" << endl;
    for (vector<int>::reverse_iterator i = v.rbegin(); i != v.rend(); ++i)
        cout << *i << " ";
    cout << endl;
    //vector::iterator为随机访问迭代器,功能最为强大，强大的表现为：
       //1.迭代器可以比较大小(位置关系比较)
       //2.迭代器可以向前向后多移动几位
       //......
    cout << "随机访问迭代器" << endl;
    for (vector<int>::iterator i = v.begin(); i < v.end(); i += 2)
        cout << *i << " ";
    cout << endl;
    //辅助函数(advance, iter_swap, distance)
    vector<int>::iterator i = v.begin();
    cout << "迭代器i一开始指向的元素为" << *i << ", ";
    advance(i, 2);
    cout << "向前移动2个位置后指向的元素为" << *i << endl;
    cout << "第一个元素和最后一个元素相差的元素个数为" << distance(v.begin(), --v.end()) << endl;
    cout << "交换第一个元素和最后一个元素的情况:" << endl;
    cout << "交换前:";
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    cout << "交换后:";
    iter_swap(v.begin(), --v.end());
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //const + 迭代器
    const auto it = v.begin(); //相当于指针常量
    //it++错误
    auto cit = v.cbegin(); //相当于指向常量的指针
    //*cit = 5错误
*/
//添加
/*
    vector<string> v;
    v.push_back("123"); //临时变量，需要调用构造函数和转移构造函数
    v.emplace_back("abc");//直接内部创建元素时作为构造函数参数，效率更高
    for (auto i : v)
        cout << i << " ";
*/
//插入（插入的位置在迭代器参数的前面
/*
    vector<string> v = { "one", "three", "four" };
    //emplace
    v.emplace(++begin(v), "two");  //std::begin(容器对象）返回容器指向第一个元素的迭代器
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //insert 单个元素
    v.insert(v.end(), "five");
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //insert 多个相同元素
    v.insert(v.begin(), 5, "zero");
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //insert 多个元素
    v.insert(v.end(), { "six", "seven", "eight" }); //初始式方法
    string s[] = { "night", "ten", "elevent" };
    v.insert(v.end(), begin(s), end(s));
    for (auto i : v)
        cout << i << " ";
*/
//删除
/*
    vector<int> v = { 0, 1, 2, 3, 3, 3, 4, 5 };
    //erase 删除单个位置元素并返回下一个元素位置(begin~end, 但不包括end)
    auto i = v.begin();
    v.erase(i);
    //++i 报错(原因:迭代器失效)
    for (auto i = v.begin(); i != v.end();) {
        if (*i == 3)
            i = v.erase(i);   //返回元素的作用
        else
            ++i;
    }
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //erase 删除一个范围元素并返回下一个元素位置
    v.erase(v.begin()+1, v.end()-1);
    for (auto i : v)
        cout << i << " ";
    cout << endl;
    //clear() 删除所有元素
    v.clear();
    for (auto i : v)
        cout << i << " ";
    cout << endl;
*/
//查找
    vector<char> v = { 'A', 'B', 'C'};
    auto it = find(v.begin(), v.end(), 'A');
    if (it != v.end())
        cout << "成功找到A";
    cout << endl;
    system("pause");
    return 0;
}