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;}};