动态数组

动态数组Vector可以动态扩展内存，其采用连续的内存空间，当内存空间不足，便以原来的容量的2倍或者1.5倍成倍的扩展，将原有的数组元素拷贝到新分配的内存空间中，释放原有的内存空间，新的元素将存入的新分配的内存空间。

示例代码

动态数组vector的size函数和capacity函数，分别作为求数组中现有的元素的个数和数组所能容纳的元素的个数。下面直接上实现的代码。
DynamicArray .h

#pragma onceclass DynamicArray {
public:DynamicArray();~DynamicArray();void push_back_Array(int value);void insertValueByPosArray(size_t pos,int value);void removeByValueFromArray(int value);void removeByPosFromArray(size_t pos);int findPosByValueArray(int value);int findValueByPosArray(size_t pos);void reclaimSpaceArray();void clearArray();int getCapacity();int getCount();void printArray();
private:int *m_pArr;size_t m_size;size_t m_capacity;
};

DynamicArray .cpp

#include "DynamicArray.h"
#include <iostream>using namespace std;
// DynamicArray.cpp DynamicArray::DynamicArray()
{m_size = 0;m_capacity = 20;m_pArr = new int[m_capacity];if (m_pArr == nullptr){cout << "new 开辟空间失败" << endl;}
}DynamicArray::~DynamicArray()
{if (m_pArr != nullptr) {delete[] m_pArr;m_pArr = nullptr;}m_size = 0;m_capacity = 0;
}void DynamicArray::push_back_Array(int value)//push_back
{if (m_pArr == nullptr){return;}reclaimSpaceArray();m_pArr[m_size] = value;m_size++;
}void DynamicArray::insertValueByPosArray(size_t pos, int value)//插入insert(可以在前，中，后插入)
{if (m_pArr == nullptr){return;}reclaimSpaceArray();for (size_t i = m_size - 1; i >= pos; --i)//pos为下标的数，从0开始{m_pArr[i + 1] = m_pArr[i];}m_pArr[pos] = value;m_size++;
}void DynamicArray::removeByValueFromArray(int value)
{if (m_pArr == nullptr){return;}int nPos = findPosByValueArray(value);removeByPosFromArray(nPos);
}void DynamicArray::removeByPosFromArray(size_t pos)//pos为下标的数，从0开始
{if (m_pArr == nullptr){return ;}if (pos < 0 || pos >= m_size)//pos的最大值为m_size-1{return ;}//找到被删除位置的下一位for (size_t i = pos + 1; i < m_size; ++i){m_pArr[i - 1] = m_pArr[i];}m_size--;
}int DynamicArray::findPosByValueArray(int value)
{size_t nPos = -1;if (m_pArr == nullptr){return nPos;}for (size_t i = 0; i < m_size; ++i){if (m_pArr[i] == value){nPos = i;break;}}return nPos;
}int DynamicArray::findValueByPosArray(size_t pos)
{if (m_pArr == nullptr){return -1;}if (pos < 0 || pos >= m_size){return -1;}return m_pArr[pos];
}void DynamicArray::reclaimSpaceArray()
{if (m_size == m_capacity){int *newArr = new int[m_capacity * 2];if (newArr == nullptr){cout << "new 开辟空间失败" << endl;return;}memset(newArr, 0, m_capacity * 2 * sizeof(int));//第三个参数为字节数memcpy(newArr, m_pArr, m_size * sizeof(int));//第三个参数为字节数//下面这种逐个赋值的方式也可以使用//for (size_t i = 0; i < m_capacity; i++)//{//	newArr[i] = m_pArr[i];//}m_capacity = m_capacity * 2;if (m_pArr) {delete[] m_pArr;m_pArr = nullptr;}m_pArr = newArr;}
}void DynamicArray::clearArray()//vector中clear()只是改变size的大小
{m_size = 0;
}int DynamicArray::getCapacity()
{return m_capacity;
}int DynamicArray::getCount()
{return m_size;
}void DynamicArray::printArray()
{for (size_t i = 0; i < m_size; ++i){//下面两种方式打印都可以cout << m_pArr[i] << " ";//int ret = findValueByPosArray(i);//cout<< ret<< " ";}cout << endl;
}

main.cpp

#include <iostream>
#include "DynamicArray.h"using namespace std;void test() {DynamicArray * pArray = new DynamicArray;int i = 0;while (i++ < 11) {pArray->push_back_Array(i);}pArray->printArray();cout <<"size= "<< pArray->getCount() << endl;cout << "容量： " << pArray->getCapacity() << endl;pArray->insertValueByPosArray(5,12);pArray->printArray();cout << "insert after size= " << pArray->getCount() << endl;cout << "insert after 容量： " << pArray->getCapacity() << endl;pArray->removeByValueFromArray(2);pArray->printArray();cout << "remove after size= " << pArray->getCount() << endl;cout << "remove after 容量： " << pArray->getCapacity() << endl;pArray->removeByPosFromArray(3);pArray->printArray();cout << "remove by pos after size= " << pArray->getCount() << endl;cout << "remove by pos after 容量： " << pArray->getCapacity() << endl;cout<<"find 2 of pos: "<<pArray->findPosByValueArray(2)<<endl;cout << "find 8 of pos: " << pArray->findPosByValueArray(8) << endl;cout << "value at pos of 6: " << pArray->findValueByPosArray(6) << endl;pArray->clearArray();cout << "size= " << pArray->getCount() << endl;cout << "容量： " << pArray->getCapacity() << endl;if (pArray){delete pArray;pArray = nullptr;}
}int main()
{test();return 0;
}