STL之手撕vector

前言

面试的时候遇到了，是从来没想过会出问题的手撕。竟然在面试环节下出了不少纰漏。

要点

• 构造函数：默认构造、拷贝构造、赋值运算符重载、移动构造函数、析构函数
• push_back/pop_back

代码

  #include <iostream>
  using namespace std;
  #define DEFAULT_CAP (200)
  class MyVector
  {
  private:
  	int* arr;
  	int size;
  	int capacity;

  	void more_capacity() {
  		capacity += DEFAULT_CAP;
  		int *tmp = new int[capacity];
  		for (int i = 0; i < size; ++i) {
  			tmp[i] = arr[i];
  		}
  		delete[] arr;
  		arr = tmp;
  		tmp = nullptr;
  		return;
  	}
  public:
  	MyVector() {
  		arr = nullptr;
  		size = 0;
  		capacity = 200;
  		return;
  	}

  	MyVector(int _size) {
  		size = _size;
  		capacity = (size < DEFAULT_CAP) ? DEFAULT_CAP : ((size - 1) / DEFAULT_CAP) * DEFAULT_CAP + DEFAULT_CAP;
  		arr = new int[capacity];
  		return;
  	}

  	MyVector(const MyVector& _v) {
  		size = _v.size;
  		capacity = _v.capacity;
  		arr = new int[capacity];
  		for (int i = 0; i < size; ++i) {
  			arr[i] = _v.arr[i];
  		}
  		return;
  	}

  	MyVector(MyVector&& _v) {
  		size = _v.size;
  		capacity = _v.capacity;
  		arr = _v.arr;
  		_v.arr = nullptr;
  		return;
  	}

  	MyVector& operator=(const MyVector& _v) {
  		if (this == &_v) {
  			return *this;
  		}
  		delete[] arr;
  		size = _v.size;
  		capacity = _v.capacity;
  		arr = new int[capacity];
  		for (int i = 0; i < size; ++i) {
  			arr[i] = _v.arr[i];
  		}
  		return *this;
  	}

  	void push_back(int val) {
  		if (size == capacity) {
  			more_capacity();
  		}
  		arr[size++] = val;
  		return;
  	}

  	void pop_back() {
  		--size;
  		return;
  	}

  	void show() {
  		cout << capacity << " " << size << " " << endl;
  	}
  };