c++ stl vector（手写版）

#include <iostream>
#include <vector>
using namespace std;
template <typename T>
class Vector {
  private:
    int capacity_;
    int size_;
    T *data_;

    void deep_copy_(int n) {
        T *tmp_dat = new T[n];
        for (int i = 0; i < size_; ++i)
            tmp_dat[i] = data_[i];
        delete[] data_;
        data_ = tmp_dat;
    }

    void fit_(int n) {
        if (capacity_ >= n) return;
        while (capacity_ < n)
            capacity_ <<= 1;
        deep_copy_(capacity_);
    }

  public:
    Vector(int n = 0, int num = 0) : size_(n), capacity_(n > 8 ? n : 8) {
        data_ = new T[capacity_];
        for (int i = 0; i < size_; ++i)
            data_[i] = num;
    }
    ~Vector() { delete[] data_; }

    void resize(int n = 0, int num = 0) {
        fit_(n);
        while (size_ < n)
            data_[size_++] = num;
    }
    void push_back(int num) {
        fit_(size_ + 1);
        data_[size_++] = num;
    }
    void pop_back() {
        if (size_) size_--;
    }

  public:
    void reserve(int n) {
        if (n > size_) capacity_ = n, deep_copy_(capacity_);
    }
    int capacity() { return capacity_; }
    void clear() { size_ = 0; }
    int size() { return size_; }
    bool empty() { return size_ == 0; }

  public:
    T &front() { return data_[0]; }
    T &back() { return data_[size_ - 1]; }
    T &operator[](int i) { return data_[i]; }

  public:
    class Iterator {
      private:
        T *p_;

      public:
    };
    T *begin() { return data_; }
    T *end() { return data_ + size_; }
};

int main() {
    Vector<int> a;
    // a.reserve(7);
    for (int i = 0; i < 1000; ++i) {
        a.push_back(i);
        printf("%d %d\n", i, a.capacity());
    }
}