侯捷 C++ 课程学习笔记：C++1级课时（零基础）

C++1级课时

一．c++初识

1.1 编写代码

#include

using namespace std;

int main(){

cout << "hello world" << endl;

return 0;

}

1.2 注释

#include

using namespace std;

int main(){

//int a = 6;

//cout << "a = " << a << endl;

return 0;

}

1.3 变量

#include

using namespace std;

int main(){

int a = 6;

cout << "a = " << a << endl;

return 0;

}

1.4 常量

#include

using namespace std;

#define day 7

//#define day = 7错误，不能有等于号

int main(){

//宏常量   #define

//day = 8;错误，常量不能改

cout << "day = " << day << endl;

const int mouth = 12;

// mouth = 13;错误，常量不能改

cout << "mouth = " << mouth << endl;

return 0;

}

变量可以修改，常量不能修改！

1.5 标识符

1. 字母，数字，下划线 组成

2. 不能是数字开头

3. 大小区分  如：ans和ANS不同

4. 不能用关键字

二.数据类型

2.1 整型

#include

using namespace std;

int main(){

short a = 5;//短整型

int b = 6;//整型

long c = 7;//长整型

long long d = 8;//长长整型

cout << "a = " << a << endl;

cout << "b = " << b << endl;

cout << "c = " << c << endl;

cout << "d = " << d << endl;

return 0;

}

2.2 sizeof关键字

#include

using namespace std;

int main(){

short a = 5;//短整型

int b = 6;//整型

long c = 7;//长整型

long long d = 8;//长长整型

cout << "short 占用内存空间：" << sizeof(short) << endl;

cout << "int 占用内存空间：" << sizeof(int) << endl;

cout << "long 占用内存空间：" << sizeof(long) << endl;

cout << "long long 占用内存空间：" << sizeof(long long) << endl;

/*

short 占用内存空间：2

int 占用内存空间：4

long 占用内存空间：4

long long 占用内存空间：8

short < int <= long <= long long;

*/

return 0;

}

2.3 实型

#include

using namespace std;

int main(){

float f1 = 3.1415926f;

cout << "f1=" << f1 << endl;

cout << "float 内存空间：" << endl;

double d1 = 1.68;

cout << "d1=" << d1 << endl;

cout << "double 内存空间：" << endl;

float f2 = 3e2;

cout << "f2=" << f1 << endl;

float f3 = 3e-2;

cout << "f3=" << f1 << endl;

return 0;

}

2.4.1 字符型

#include

using namespace std;

int main(){

char ch1 = 'a';

cout << "ch1=" << ch1 << endl;

cout << "char字符在内存当中的占位空间大小：" << sizeof(char) << endl;

// char ch2 = "a";//错误

// char ch3 = 'abc';//错误

char ch4 = 'A';

cout << "A的ASCII码" << (int)ch4 << endl;

char ch5 = 97;

cout << "ch5: " << ch5 << endl;

/*

a = 97

A = 65

0 = 48

*/

return 0;

}

2.4.2 字符型ASCII码

2.4.3 字符型应用

/*1.获取字符的ＡＳＣＩＩ码

#include

using namespace std;

int main(){

char ch = 'a';

int n1 = ch;

int n2 = (int)ch;

int n3 = int(ch);

cout << "n1 = " << n1 << endl;

cout << "n2 = " << n2 << endl;

cout << "n3 = " << n3 << endl;

return 0;

}

*/

/*2.整数转成字符

#include

using namespace std;

int main(){

int n = 65;

char ch1 = 'A';

char ch2 = (char)n;

char ch3 = char(n);

cout << "n1 = " << n1 << endl;

cout << "n2 = " << n2 << endl;

cout << "n3 = " << n3 << endl;

return 0;

}

*/

/*3.大小写转换/1大写转小写

#include

using namespace std;

int main(){

char ch1 = 'A';

char xx = ch1 + 32;

cout << "xx = " << xx << endl;

return 0;

}*/

/*3.大小写转换/2小写转大写

#include

using namespace std;

int main(){

char ch2 = 'a';

char dx = ch2 + 32;

cout << "dx = " << dx << endl;

return 0;

}  

*/

/*4.字符移动

#include

using namespace std;

int main(){

char ch1 = 'f';

char ch2 = ch1 - 2;

cout << "ch2 = " << ch2 << endl;

char ch3 = 'd';

char ch4 = ch3 + 2;

cout << "ch4 = " << ch4 << endl;

return 0;

}  

*/

2.5 转义字符

/*

\t(水平制表HT)

下一个ＴＡＢ

\n(换行LF)

将当前位置移动到下一行开头

\r(回车CR)

将当前位置移动到本行开头

\b(退格BS)

将当前位置移动到前一列

\v(垂直制表VT)

\\        

一个反斜线字符\

\'

一个单引号(撇号)字符'

\"

一个双引号字符"

\?()

一个问号？

*/

#include

using namespace std;

int main(){

//换行

// cout << "hello world\ngogogo!" << endl;

cout << "hello world" << endl;

cout << "gogogo!" << endl;

//水平制表符

cout << "aaaaa\thello world" << endl;

cout << "aa\thello world" << endl;

cout << "aaa\thello world" << endl;

return 0;

}

2.6 字符串型

#include

using namespace std;

int main(){

char ch = 'a';

char str1[] = "abc";

cout << str1 << endl;

string str2 = "def";

cout << str2 << endl;

return 0;

}

2.7 布尔类型bool

/*char

true      本质为1，非0即为真

false     本质为0

*/

//bool类型占1字节大小

#include

using namespace std;

int main(){

bool flag = true;//1

cout << flag << endl;

flag = false;//0

cout << flag << endl;

cout << "size of bool = " << sizeof(bool) << endl;//1

return 0;

}  

2.8 数据的输入

#include

using namespace std;

int main(){

//1.整型

int a1;

cout << "请输入a的值，a = " << endl;

cin >> a1;

cout << "a = " << a1 << endl;

int a2,b2;

cout << "请输入a和b的值：" << endl;

cin >> a2 >> b2;

cout << "a = " << a2 << endl;

cout << "b = " << b2 << endl;

//2.浮点数

float f;

cout << "请输入f的值，f = " << endl;

cin >> f;

cout << "f = " << f << endl;  

//3.字符型

char ch;

cout << "请输入ch的值，ch = " << endl;

cin >> ch;

cout << "ch = " << ch << endl;   

//4.字符串

string str;

cout << "请输入str的值，str = " << endl;

cin >> str;

cout << "str = " << str << endl;  

//5.布尔类型bool,输入的时候，不要输入true和false，应该输入1和0

bool flag;

cout << "请输入flag的值，flag = " << endl;

cin >> flag;

cout << "flag = " << flag << endl;

return 0;

}

2.9 数据类型的转换

#include

using namespace std;

int main(){

// string str = "abc";

// int a = (int)str;  //报错

// cout << a << endl;

// string str = "123";

// int a = (int)str;  //报错

// cout << a << endl;

// int a = 123;

// string str = (string)a;  //报错

// cout << str << endl;

// float a = 123.33;

// string str = (string)a;  //报错

// cout << str << endl;

float a0 = 123.33;

int x0 = (int)a0;      //正确

cout << "a = " << a0 << endl;

cout << "x = " << x0 << endl;

bool a = false;

int x = (int)a;      //正确

cout << "x = " << x << endl;

int x1 = 5;

bool a1 = (bool)x1;      //正确

cout << "a = " << a1 << endl;

int y = 0;

bool b = (bool)y;      //正确

cout << "b = " << b << endl;

float f = 3.56;

bool a4 = (bool)f;      //正确

cout << "a = " << a4 << endl;

char a2 = 'a';

int x2 = (int)a2;      //正确

cout << "x = " << x2 << endl;

int y1 = 65;

char b3 = y1;

cout << "b = " << b3 << endl;

int z = 97;

char c = z;

cout << "c = " << c << endl;

int a5 = 6;

int b5 = 5;

int c0 = a5/b5;

cout << "c = "<< c0 << endl;

return 0;

}

2.10 科学计数法

#include

using namespace std;

int main(){

float f1 = 3.3e-2;

cout << f1 << endl;

float f2 = 3.3e2;

cout << f2 << endl;

float a1 = 123456;

cout << "a1 = " << a1 << endl; //输出a1 = 123456（正常输出）

float a2 = 1234567;

cout << "a2 = " << a2 << endl; //输出a2 = 1.23457e+006（科学计数法输出）

return 0;

}

2.11 unsigned关键字

#include

using namespace std;

int main(){

unsigned a;

a = 1;

cout << "a = " << a << endl;

signed int b;

b = -1;

cout << "b = " << b << endl;

return 0;

}

---------------------------------------------------------------------------------------------------------------------------------

1	2	3
正确	正确	正确

作业

2-1   a+b的和

代码：1.数据结构\1-1   a+b的和.cpp

实现：1.数据结构\1-1   a+b的和.exe

2-2   将int a 转换成 char str

代码：1.数据结构\1-2   将int a 转换成 char str.cpp

实现：1.数据结构\1-2   将int a 转换成 char str.exe

2-3   大小写转换(大转小)

代码：1.数据结构\1-3   大小写转换(大转小).cpp

实现：1.数据结构\1-3   大小写转换(大转小).exe

三．运算符

3.1 算数运算符

3.1.1   示例1-示例2

#include

using namespace std;

int main(){

int a = 10,b = 3;

cout << "a+b = " << a+b << endl;

cout << "a-b = " << a-b << endl;

cout << "a*b = " << a*b << endl;

cout << "a/b = " << a/b << endl;

cout << "a/b = " << (float)a/(float)b << endl;

int a1 = 10,b1 = 3;

cout << "a1 % b1 = " << a1 % b1 << endl;

int a2 = 3;b2 = 10;

cout << "a2 % b2 = " << a2 % b2 << endl;

//只有整型变量可以进行取模

return 0;

}

3.1.2   示例3

#include

using namespace std;

int main(){

//前置递增

int a1 = 10;

++a1;

cout << "a1 = " << a1 << endl;

//后置递增

int a2 = 10;

a2++;

cout << "a2 = " << a2 << endl;

//前置递增与后置递增的区别

int a3 = 10;

int b3 = ++a3 * 10;

cout << "a3 = " << a3 << endl;

cout << "b3 = " << b3 << endl;

int a4 = 10;

int b4 = a4++ * 10;

cout << "a4 = " << a4 << endl;

cout << "b4 = " << b4 << endl;

/*

前置递增:先递增,再参与运算

后置递增:先参与运算,再递增

*/

}

3.2 赋值运算符

#include

using namespace std;

int main(){

//赋值

int a = 10,b = 20;

a = b;

cout << "（赋值）a = " << a << endl;

cout << "（赋值）b = " << b << endl;

//+=

int a1 = 10,b1 = 20;

a1 += b1;

cout << "（+=）a = " << a1 << endl;

cout << "（+=）b = " << b1 << endl;

//-=

int a2 = 20,b2 = 10;

a2 -= b2;

cout << "（-=）a = " << a2 << endl;

cout << "（-=）b = " << b2 << endl;

return 0;

}

3.3 比较运算符

#include

using namespace std;

int main(){

int a = 4,b = 3;

//== 等于

cout << (a == b) << endl;

//!= 不等于

cout << (a != b) << endl;

//> 大于

cout << (a > b) << endl;

//< 小于

cout << (a < b) << endl;

//>= 大于等于

cout << (a >= b) << endl;

//<= 小于等于

cout << (a <= b) << endl;

/*

真      '1'

假 '0'

*/

return 0;

}

3.4 逻辑运算符

 #include

using namespace std;

int main(){

//!非

int a = 0;

cout << "（!非）!a = " << (!a) << endl;

//a&&b  都为真

int a1 = 0,b1 = 0;

cout << "（a&&b）a&&b = " << (a1&&b1)<< endl;

//  ||  或

int a2 = 1,b2 = 1;

cout << "（||）a||b= " << (a2||b2) << endl;

return 0;

}

3.5 三目运算符

#include

using namespace std;

int main(){

int a = 10;

int b = a<5?1:0;

cout << "a = " << a << endl;

cout << "b = " << b << endl;

return 0;

}

3.6 拓展-格式化输入输出

3.6.1  scanf输入

#include

using namespace std;

int main(){

/*

int scanf("%d",&n);

long scanf("%ld",&n);

long long scanf("%lld",&n);

float scanf("%f",&n);

double scanf("%lf",&n);

char scanf("%c",&ch);

char数组 scanf("%s",arr);//arr表示地址，不用&

*/

return 0;

}

数据类型	格式化表达式
int	scanf("%d",&n);
long	scanf("%ld",&n);
long long	scanf("%lld",&n);
float	scanf("%f",&n);
double	scanf("%lf",&n);
char	scanf("%c",&ch);
char数组	scanf("%s",arr);//arr表示地址，不用&

3.6.2  printf输出

#include

using namespace std;

int main(){

cout << "==============int :" << endl;

int a;

scanf("%d",&a);

printf("%6d",a);  //加宽度，左补空格

printf("%06d",a); //加宽度，左补零

printf("%d",a);

cout << "==============long :" << endl;

long b;

scanf("%ld",&b);

printf("%ld\n",b);

cout << "==============long long :" << endl;

long long c;

scanf("%lld",&c);

printf("%lld\n",c);

cout << "==============float 默认小数位6位:" << endl;

float f1;

scanf("%f",&f1);

printf("%.3f\n",f1);

cout << "==============float 保留3位小数位:" << endl;

printf("%f\n",f1);

cout << "==============double 默认小数位6位:" << endl;

double d1;

scanf("%lf",&d1);

printf("%.f\n",d1);

cout << "==============double 保留4位小数位:" << endl;

printf("%.4f\n",d1);

cout << "==============char:" << endl;

char ch;

scanf("%c",&ch);

printf("%c\n",ch);

cout << "==============char[]:" << endl;

char str[10];

scanf("%s",&str);

printf("%s\n",str);

return 0;

}

数据类型	格式化表达式
int	printf("%d",a);
long	printf("%ld",a);
long long	printf("%lld",a);
float	printf("%f",a);
double	printf("%.f",a);
char	printf("%c,ch);
char数组	printf("%s",arr);//arr表示地址，不用&

3.6.3  设置宽度与对齐

3.6.4  按八进制和十六进制输入输出

3.7  cout保留小数位

3.8  拓展-常用的数字函数

3.9  拓展-数学补充

3.10 拓展-c++万能头文件

万能头：#include

3.11 拓展-程序示例

1.级数求和

#include

using namespace std;

int main(){

int k,n;

double sn=0.0;

scanf("%d",&k);

for(n=1;;n++){

 sn+=1.0/n;

 if(sn>k*1.0)

  break;

    }

printf("%d",n);

return 0;

}