C++对C的扩充
示例：
1.C++中的bool类型示例
#include <iostream>
using namespace std;
int main()
{
bool b1=10;
bool b2=0;
bool b3=-10;
cout << "b1=" << b1 << endl; //1
cout << "b2=" << b2 << endl; //0
cout << "b3=" << b3 << endl; //1
bool b4=true;
bool b5=false;
cout << "b4=" << b4 << endl; //1
cout << "b5=" << b5 << endl; //0
cout << boolalpha << "b1=" << b1 << endl; //true
cout << boolalpha << "b2=" << b2 << endl; //false
cout << noboolalpha << "b4=" << b4 << endl; //1
cout << noboolalpha << "b5=" << b5 << endl; //0
return 0;
}
运行结果：
2.引用（reference）示例
#include <iostream>
using namespace std;
int main()
{
int num = 520; //定义一个普通变量
//int &ref; //定义引用时，如果不初始化，直接报错
int &ref1 = num; //此时ref1引用的目标为num
//引用与其目标的数据是同步的
cout<<"num = "<<num<<" ref1 = "<<ref1<<endl; //对数据可读
num = 1314; //更改目标， 引用跟着变化
cout<<"num = "<<num<<" ref1 = "<<ref1<<endl; //对数据可读
ref1 = 999; //更改引用， 目标跟着改变 对数据可写
cout<<"num = "<<num<<" ref1 = "<<ref1<<endl; //对数据可读
//引用与其目标的地址是一致的
cout<<"&num = "<<&num<<" &ref1 = "<<&ref1<<endl; //地址相同
//引用与其目标内存大小是一致的
cout<<"sizeof num = "<<sizeof(num)<<" sizeof ref1 = "<<sizeof(ref1)<<endl; //对数据可读
//引用与其目标的类型是一致的
cout<<"typeid.name num = "<<typeid(num).name()<<" typeid.name ref1 = "<<typeid (ref1).name()<<endl;
//验证引用的目标一旦指定，后期就无法进行更改
int key = 333; //新的普通变量
ref1 = key; //该语句不报错，执行的结果为将key的值，赋值给ref1也就是赋值给num
//&ref1 = key; //给地址赋值，报错
//int &ref1 = key; //引用重定义
//一个目标可以定义多个引用
int &ref2 = num;
cout<<"&num = "<<&num<<" &ref1 = "<<&ref1<<" &ref2 = "<<&ref2<<endl; //地址相同
//可以给 引用定义一个引用
int &ref3 = ref1;
cout<<"&num = "<<&num<<" &ref1 = "<<&ref1<<" &ref2 = "<<&ref2<<" &ref3 = "<<&ref3<<endl; //地址相同
//引用与引用的目标类型不一致时会报错
//double &ref4 = num;
//定义指针的引用
int *ptr = # //定义一个指针
int * &ptrRef = ptr; //定义的是指针的引用
cout<<"num = "<<num<<" *ptr = "<<*ptr<<" *ptrRef = "<<*ptrRef<<endl;
//定义数组的引用
int arr[5] = {1,2,3,4,5};
int (&arrRef)[5] = arr;
// for(int val:arrRef)
// {
// cout<<val<<" ";
// }
for(int i=0; i<5; i++)
{
cout<<arrRef[i]<<" "; //cout<<arr[i]<<" ";
}
cout<<endl;
cout<<"sizeof arrRef = "<<sizeof (arrRef)<<endl; //20
return 0;
}
运行结果：
3.引用作为函数参数示例
#include <iostream>
using namespace std;
//自定义交换函数1
void swap_1(int n, int k)
{
//交换三部曲
int temp = n;
n = k;
k = temp;
cout<<"swap_1:: n = "<<n<<" k = "<<k<<endl; //1314 520
}
//自定义交换函数2
void swap_2(int *ptr, int *qtr)
{
//交换三部曲
int *temp = ptr;
ptr = qtr;
qtr = temp;
cout<<"swap_2::*ptr = "<<*ptr<<" *qtr = "<<*qtr<<endl; //1314 520
}
//自定义交换函数3
void swap_3(int *ptr, int *qtr)
{
//交换三部曲
int temp = *ptr;
*ptr = *qtr;
*qtr = temp;
cout<<"swap_2::*ptr = "<<*ptr<<" *qtr = "<<*qtr<<endl; //1314 520
}
//自定义交换函数4
void swap_4(int &n, int &k)
{
//交换三部曲
int temp = n;
n = k;
k = temp;
cout<<"swap_4:: n = "<<n<<" k = "<<k<<endl; //520 1314
}
int main()
{
int num = 520;
int key = 1314;
//调用函数1，完成两个数的交换
swap_1(num, key);
cout<<"main:: num = "<<num<<" key = "<<key<<endl; //520 1314
//调用函数2，完成两个数的交换
swap_2(&num, &key);
cout<<"main:: num = "<<num<<" key = "<<key<<endl; //520 1314
//调用函数3，完成两个数的交换
swap_3(&num, &key);
cout<<"main:: num = "<<num<<" key = "<<key<<endl; //1314 520
//调用函数4，完成两个数的交换
swap_4(num, key);
cout<<"main:: num = "<<num<<" key = "<<key<<endl; //520 1314
return 0;
}
运行结果：
4.数组引用作为函数参数示例
#include <iostream>
using namespace std;
//定义函数进行冒泡排序
//void my_sort(int brr[], int n)
//{
// cout<<sizeof(brr)<<endl; //虽然使用的是数组名进行接收，但是本质上还是指针
//}
//定义函数进行冒泡排序
//void my_sort_1(int *ptr, int n)
//{
// cout<<sizeof(ptr)<<endl; //4
//}
//定义函数进行冒泡排序
void my_sort(int (&arrRef)[5])
{
cout<<sizeof (arrRef)<<endl; // 接收的就是主调函数中的数组本身
cout<<"arrRef = "<<arrRef<<endl; //地址
for(int i=1; i<5; i++)
{
for(int j=0; j<5-i; j++)
{
if(arrRef[j] > arrRef[j+1])
{
//交换
int temp = arrRef[j];
arrRef[j] = arrRef[j+1];
arrRef[j+1] = temp;
}
}
}
}
int main()
{
int arr[5] = {3,2,1,4,5};
cout<<"arr = "<<arr<<endl;
//调用函数进行冒泡排序
my_sort(arr);
//输出排序后的结果
for(int val : arr)
{
cout<<val<<" ";
}
cout<<endl;
return 0;
}
运行结果：
5.常引用（const）示例
#include <iostream>
using namespace std;
int my_max(const int &m, const int &n)
{
return m>n?m:n;
}
int main()
{
int num = 520;
int key = 1314;
cout<<my_max(num, key)<<endl; //1314
cout<<my_max(520, 1314)<<endl;
return 0;
}
运行结果：
6.单个内存空间的申请与释放示例
#include <iostream>
using namespace std;
int main()
{
//在堆区申请一个int类型的空间大小
int *p1 = new int; //int *p1 = (int *)malloc(sizeof(int));
cout<<"*p1 = "<<*p1<<endl; //随机值
*p1 = 520;
cout<<"*p1 = "<<*p1<<endl; //520
//在堆区申请空间顺便对空间中的数据进行初始化
double *p2 = new double(3.14);
cout<<"*p2 = "<<*p2<<endl; //3.14
//在堆区申请空间顺便对空间中的数据进行初始化
double *p3 = new double{56.789};
cout<<"*p3 = "<<*p3<<endl; //56.789
//释放 堆区空间
delete p1;
delete p2;
delete p3;
p1 = NULL;
p2 = NULL;
p3 = NULL;
return 0;
}运行结果：
7.连续空间的申请和释放示例
#include <iostream>
using namespace std;
int main()
{
int *p1 = new int[5]; //堆区连续申请5个int类型的空间
for(int i=0; i<5; i++) //如果不初始化默认为随机值
{
cout<<*(p1+i)<<" ";
}
cout<<endl;
//使用堆区空间，对堆区空间进行写操作
for(int i=0; i<5; i++) //如果不初始化默认为随机值
{
*(p1+i) = 10+i;
}
cout<<endl;
for(int i=0; i<5; i++) //如果不初始化默认为随机值
{
cout<<*(p1+i)<<" ";
}
cout<<endl;
//堆区连续申请空间并对其进行初始化
int *p2 = new int[5]{5,7,3,4,8};
for(int i=0; i<5; i++) //如果不初始化默认为随机值
{
cout<<*(p2+i)<<" ";
}
cout<<endl;
//释放堆区空间
delete []p1;
delete [] p2;
p1 = NULL;
p2 = NULL;
return 0;
}运行结果：
8.练习：要求在堆区申请5个double类型的空间，用于存储5名学生的成绩。请自行封装函数完成
1> 空间的申请
2> 学生成绩的录入
3> 学生成绩的输出
4> 学生成绩进行降序排序
5> 释放申请的空间
主程序中用于测试上述函数
#include <iostream>
using namespace std;
void shuru(double *p1){
for(int i=0;i<5;i++){
cout<<"shuru>>";
cin>>p1[i];
}
}
void shuchu(double * &p1){
for(int i=0;i<5;i++){
cout<<p1[i]<<" ";
}
}
void paixu(double *p1,double n){
for(int i=1;i<n;i++){
for(int j=0;j<n-i;j++){
if(p1[j]<p1[j+1]){
int temp=p1[j];
p1[j]=p1[j+1];
p1[j+1]=temp;
}
}
}
}
int main()
{
double *p1=new double [5];
if(p1 == NULL)
{
return -1;
}
shuru(p1);
cout<<endl;
shuchu(p1);
paixu(p1,5);
cout<<endl;
shuchu(p1);
delete []p1;
p1=NULL;
return 0;
}
运行结果：
知识梳理：
