c++手写vector

好的，这是手写 vector 的代码示例：

#include <iostream>
#include <memory>

template <typename T>
class MyVector {
public:
    MyVector() : size_(0), capacity_(8) {
        data_ = std::make_unique<T[]>(capacity_);
    }

    ~MyVector() {
        clear();
    }

    void push_back(const T& value) {
        if (size_ == capacity_) {
            reserve(capacity_ * 2);
        }
        data_[size_++] = value;
    }

    void pop_back() {
        if (size_ > 0) {
            --size_;
        }
    }

    void clear() {
        size_ = 0;
        capacity_ = 8;
        data_.reset(new T[capacity_]);
    }

    void reserve(int new_capacity) {
        if (new_capacity <= capacity_) {
            return;
        }
        std::unique_ptr<T[]> new_data = std::make_unique<T[]>(new_capacity);
        for (int i = 0; i < size_; ++i) {
            new_data[i] = data_[i];
        }
        data_ = std::move(new_data);
        capacity_ = new_capacity;
    }

    T& operator[](int index) {
        return data_[index];
    }

    const T& operator[](int index) const {
        return data_[index];
    }

    int size() const {
        return size_;
    }

    int capacity() const {
        return capacity_;
    }

private:
    int size_;
    int capacity_;
    std::unique_ptr<T[]> data_;
};

int main() {
    MyVector<int> vec;
    for (int i = 0; i < 10; ++i) {
        vec.push_back(i);
    }
    for (int i = 0; i < vec.size(); ++i) {
        std::cout << vec[i] << " ";
    }
    std::cout << std::endl;
    vec.pop_back();
    for (int i = 0; i < vec.size(); ++i) {
        std::cout << vec[i] << " ";
    }
    std::cout << std::endl;
    vec.clear();
    for (int i = 0; i < 10; ++i) {
        vec.push_back(i);
    }
    vec.reserve(20);
    for (int i = 0; i < vec.size(); ++i) {
        std::cout << vec[i] << " ";
    }
    std::cout << std::endl;
    return 0;
}