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
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#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
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#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
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#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;} |
运行环境
以上代码的运行环境为：vs2017控制台输出程序。
运行效果
以上仅供记录。可帮助理解vector。
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原文链接：https://blog.csdn.net/blqzj214817/article/details/125315822
