【C++】STL之vector类

vector类，相当于不定长的数组，并与其一样支持随机访问。

 

vector的初始化：

vector<int> v{1,2,3,4,5}; // 列表初始化
vector<int> v2(5,0); // v2含有5个元素，每个都是0

 

一些操作：

vec.push_back(val); // 在末尾插入一个元素
vec.pop_back(val); // 弹出末尾的一个元素
vec.front() // 获取首元素
vec.back() // 获取末尾元素
vec.size() // 返回大小
vec.empty // 返回是否为空
vec.clear(); // 清空

 

迭代器：

vector<int>::iterator itB = v1.begin();
cout << "The first element of the vector is " << *itB << '\n';    
vector<int>::iterator itE = v1.end();
cout << "The last element of the vector is " << *(itE - 1) << '\n' << endl;

反向迭代器：

auto itRB = v1.rbegin(), itRE = v1.rend();
cout << "The first element of the vector is " << *(itRE - 1) << '\n';
cout << "The last element of the vector is " << *(itRB) << '\n' << endl;

 

排序：

vector<int> v2{ 2,1,5,3,4 };
sort(v2.begin(), v2.end());

 

去重：

vector<int> v3{ 1,1,1,2,2,3 };
// unique()函数返回一个迭代器，指向重复元素的开头
auto ituv=unique(v3.begin(), v3.end());
//用erase函数擦除重复的元素
v3.erase(ituv, v3.end());

 

一段测试代码：

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
using namespace std;
void show(vector<int> v) {
    for (auto i : v) {
        cout << i << ' ';
    }
    cout << endl;
}
void fill(vector<int> v) {
    for (int i = 1; i <= 10; i++) {
        v.push_back(i);
    }
}
int main(void)
{
    ios::sync_with_stdio(false);
    cin.tie(false);

    vector<int> v1;
        
    fill(v1);

    cout << "The first element of the vector is " << v1.front() << '\n';
    cout << "The last element of the vector is " << v1.back() << '\n';
    cout << "The size of the vector is " << v1.size() << '\n' << endl;

    cout << "The vector is" << (v1.empty() ? " " : " not ") << "empty." << "\n";
    v1.clear();
    cout << "The vector is" << (v1.empty() ? " " : " not ") << "empty." << "\n" << endl;

    fill(v1);

    vector<int>::iterator itB = v1.begin();
    cout << "The first element of the vector is " << *itB << '\n';
    vector<int>::iterator itE = v1.end();
    cout << "The last element of the vector is " << *(itE - 1) << '\n' << endl;
    // 反向迭代器
    auto itRB = v1.rbegin(), itRE = v1.rend();
    cout << "The first element of the vector is " << *(itRE - 1) << '\n';
    cout << "The last element of the vector is " << *(itRB) << '\n' << endl;

    vector<int> v2{ 2,1,5,3,4 };
    sort(v2.begin(), v2.end());
    show(v2);

    vector<int> v3{ 1,1,1,2,2,3 };
    // unique()函数返回一个迭代器，指向重复元素的开头
    auto ituv=unique(v3.begin(), v3.end());
    v3.erase(ituv, v3.end());
    show(v3);
    
    return 0;
}