1.空指針 int * p = NULL;
指向內存中編號爲0的空間,用來初始化指針變量, 其指向的內存是不可訪問的(因爲0~255間的內存編號由系統佔用)。
注:
指針前加*表示解引用,用來找到該指針指向的內存中的數據。所以當形參是 &引用或指針的指針** 時,改變形參就是改變實參。
2.野指針
指向非法的內存空間。野指針和空指針都不是我們申請的空間,故無法訪問。
3.const修飾指針有3種情況
(1)const修飾指針——常量指針
指針的指向可改,指向的值不可改。
(2)const修飾常量——指針常量
指針的指向不可改,指向的值可改。
(3)const既修飾指針,又修飾常量
指針的指向與指向的值都不可改。
例:
4. 值傳遞只改變形參,不影響實參。地址傳遞都影響。
5.通過結構體指針訪問結構體裏的屬性,需要利用‘—>’
6.把函數中的形參改爲指針,可以大幅減少內存空間的佔用,不會複製新的副本出來
7.結構體使用const
8. 項目實戰 —— 通訊錄管理系統
#include <iostream>
using namespace std;
#include <string>
#define MAX 1000
//設計聯繫人結構體
struct Person
{
string m_Name;
int m_Sex;
int m_Age;
string m_Phone;
string m_Addr;
};
//設計通訊錄結構體
struct Addressbooks
{
struct Person personArray[MAX];//通訊錄保留的聯繫人數組
int m_Size;//通訊錄當前記錄的聯繫人個數
};
//1、添加聯繫人
void addPerson(Addressbooks* abs)
{
if(abs->m_Size == MAX)
{
cout << "通訊錄已滿,無法添加!\n" ;
return;
}
else
{
//姓名
string name;
cout << "請輸入姓名: \n";
cin >> name;
abs->personArray[abs->m_Size].m_Name = name;
//性別
cout << "請輸入性別: \n";
cout << "1 --- 男 \n";
cout << "2 --- 女 \n";
int sex = 0;
while (1)
{
cin >> sex;
if(sex==1 || sex==2)
{
abs->personArray[abs->m_Size].m_Sex = sex;
break;
}
else
cout << "輸入有誤,請重新輸入! \n";
}
//年齡
cout << "請輸入年齡: \n";
int age = 0;
cin >> age;
abs->personArray[abs->m_Size].m_Age = age;
//電話
cout << "請輸入電話: \n";
string phone;
cin >> phone;
abs->personArray[abs->m_Size].m_Phone = phone;
//住址
cout << "請輸入住址: \n";
string address;
cin >> address;
abs->personArray[abs->m_Size].m_Addr = address;
//更新通訊錄的當前人數
abs->m_Size++;
cout << "添加成功!\n";
// system("pause");//請按任意鍵繼續
// system("cls");//清屏
}
}
//2、顯示所有聯繫人
void showPerson(Addressbooks* abs)
{
if(abs->m_Size == 0)
cout << "當前記錄爲空 \n";
else
for(int i = 0; i < abs->m_Size; i++)
{
cout << "姓名" << abs->personArray[i].m_Name << "\t";
cout << "性別" << abs->personArray[i].m_Sex << "\t";
cout << "年齡" << abs->personArray[i].m_Age << "\t";
cout << "電話" << abs->personArray[i].m_Phone << "\t";
cout << "住址" << abs->personArray[i].m_Addr << endl;
}
// system("pause");
// system("cls");
}
//判斷指定聯繫人是否存在
int isExist(Addressbooks* abs, string name)
{
for(int i = 0; i < abs->m_Size; i++)
if(abs->personArray[i].m_Name == name)
return i;//找到
return -1;//沒找到
}
//3、刪除指定聯繫人
void deletePerson(Addressbooks* abs)
{
cout << "請輸入刪除聯繫人姓名: \n";
string name;
cin >> name;
int ret = isExist(abs,name);
if(ret != -1)
{
//找到此人,做刪減
for(int i = ret; i < abs->m_Size; i++)
abs->personArray[i] = abs->personArray[i+1];//數據依次前移
abs->m_Size--;//實時更新通訊錄上的人數
cout << "刪除成功!\n";
}
else
cout << "查無此人\n";
// system("pause");
// system("cls");
}
//4、查找指定聯繫人
void findPerson(Addressbooks* abs)
{
cout << "請輸入您要查找的聯繫人: \n";
string name;
cin >> name;
int ret = isExist(abs,name);
if(ret != -1)
{
cout << "姓名: " << abs->personArray[ret].m_Name << "\t";
cout << "性別: " << abs->personArray[ret].m_Sex << "\t";
cout << "年齡: " << abs->personArray[ret].m_Age << "\t";
cout << "電話: " << abs->personArray[ret].m_Phone << "\t";
cout << "住址: " << abs->personArray[ret].m_Addr << endl;
}
else
cout << "查無此人\n";
// system("pause");
// system("cls");
}
//5、修改指定聯繫人
void modifyPerson(Addressbooks* abs)
{
cout << "請輸入您要修改的聯繫人: \n";
string name;
cin >> name;
int ret = isExist(abs,name);
if(ret != -1)
{
string name;
cout << "請輸入姓名:\n";
cin >> name;
abs->personArray[ret].m_Name = name;
cout << "請輸入性別:\n";
cout << "1 --- 男\n";
cout << "2 --- 女\n";
int sex = 0;
while (1)
{
cin >> sex;
if(sex == 1 || sex == 2)
{
abs->personArray[ret].m_Sex = sex;
break;
}
cout << "輸入有誤,請重新輸入!\n";
}
int age = 0;
cout << "請輸入年齡:\n";
cin >> age;
abs->personArray[ret].m_Age = age;
string phone;
cout << "請輸入電話:\n";
cin >> phone;
abs->personArray[ret].m_Phone = phone;
string address;
cout << "請輸入地址:\n";
cin >> address;
abs->personArray[ret].m_Addr = address;
cout << "修改成功!\n";
}
else
cout << "查無此人\n";
// system("pause");
// system("cls");
}
//6、清空聯繫人
void cleanPerson(Addressbooks* abs)
{
abs->m_Size = 0;
cout << "通訊錄已清空 \n";
// system("pause");
// system("cls");
}
void ShowMenu()
{
cout << "***************************" << endl;
cout << "***** 1、添加聯繫人 *****" << endl;
cout << "***** 2、顯示聯繫人 *****" << endl;
cout << "***** 3、刪除聯繫人 *****" << endl;
cout << "***** 4、查找聯繫人 *****" << endl;
cout << "***** 5、修改聯繫人 *****" << endl;
cout << "***** 6、清空聯繫人 *****" << endl;
cout << "***** 0、退出通訊錄 *****" << endl;
cout << "***************************" << endl;
}
int main()
{
Addressbooks abs;
abs.m_Size = 0;
int select = 0;
while (1)
{
ShowMenu();
cin >> select;
switch (select)
{
case 1://添加
addPerson(&abs);//地址傳遞,修改實參
break;
case 2://顯示
showPerson(&abs);
break;
case 3://刪除
deletePerson(&abs);
break;
case 4://查找
findPerson(&abs);
break;
case 5://修改
modifyPerson(&abs);
break;
case 6://清空
cleanPerson(&abs);
break;
case 0:
cout << "歡迎下次使用" << endl;
return 0;
default:
break;
}
}
}