分类： C++

//5-1-1 math symbols

#include <iostream>

using namespace std;

int main() {

int a = 1;

int b = 3;

cout << a+b << endl;

cout << a – b << endl;

cout << a * b << endl;

cout << a / b << endl; //if int divide int, there will be int too

cout << a*1.0 / b << endl;//if int multiple float before divide, there will be float

a = 10000000;

b = 100000;

cout << a * b << endl; //output will out the range of int

cout << (long long)a * b << endl; //we can translate it forcely

a = -1;

b = 2;

cout << a / b << endl;//just cut of the dot number

a = +1;

b = -a;

int c = -(-a);

cout << a <<‘ ‘ << b <<‘ ‘ << c << endl;//postive & negative

char A = ‘A’;

A = A + 1;

A = A + 24;

cout << A << endl;

return 0;

}

//5-1-2 mod % symbol

#include <iostream>

using namespace std;

int main(){

int a = 100;

int b = 9;

cout << a % b << endl; //1

a = 100;

b = -9;

cout << a % b << endl; //1

a = -100;

b = 9;

cout << a % b << endl;//the mod symbol %;-100 % 9 is  9*-11 (near 0 direction) not -12 in C/C++ launguage

//-1

a = -100;

b = -9;

cout << a % b << endl; //-100 -(-9)*11=-1

//-1

//1、the symbol of mod is the same as the be devided number

//first we should take the negative symbol from the  be devided number 

//second we use it as 100 = -9 * （-11） + 1 

//third the left +1 is the lease number and add the negative symbol – to the 1

//fourth the final answer is  -1

return 0;

}

//5 – 1-3 ++ & –symbol

#include <iostream>

using namespace std;

int main() {

int a = 6; 

a++; //a=a+1

cout << a << endl;

++a; //a=a+1

cout << a << endl;

//the same in the two ways

int j = 8;

int x = a++; //first give the value to x, then add 1 to a

int y = ++j; //first add 1 to the value , then give the value to y (this type is more effective)

cout << x << endl; 

cout << y << endl;

int z = (a++) + (++a);//9+11=20 we must not to write this type code ,because it will make a big problem

cout << z << endl;

a–; //a=a-1

cout << a << endl;

–a;//a=a-1

cout << a << endl; 

}

//5 – 2 valued symbols

#include <iostream>

using namespace std;

int main() {

int x = 9;

int y = 6;

x = y; // let y to x

cout << x << endl;

x += y; //x=x+y   the length is 10 bytes to 7 bytes

cout << x << endl;

x -= y; //x=x-y

cout << x << endl;

x *= y; //x=x*y

cout << x << endl;

x /= y; //x=x/y

cout << x << endl;

x %= y; //x=x%y

cout << x << endl;

return 0;

}

#include <iostream>

using namespace std;

int main() {

char a = ‘y’; //use the single quotes can be recognized the char type

char b = ‘z’;

//char a =”y”;//using double quotes can be recognized as a lot of string

cout << a << endl;

cout << int(a) << endl; //cause 1 byte can be 1*2^8=256 ,so that can be include ascii symbol

//cout << b – a << endl;

b = 121;

cout << b << endl;

cout << sizeof(a) << endl;

cout << sizeof(char) << endl;

return 0;

}

Day4 October 10 2025

//4-5 translate words

#include <iostream>

using namespace std;

int main() {

char a = ‘\a’;

char n = ‘\n’; //ascii = 7 , which is \a and would make a beep sound

cout << int(a) << endl;

cout << “Vito \”Al\”\\gorith\088m Union\tV\0ito” << n; // \n as a key words change the line;\t is tab ;\\can output a \;\0 will cut out;

//\” can output the ” normally

return 0;

}

/*

\0xx is a octal(8 position rule)

\088 would not recognized a real function

\077 is a ? symbol

*/

//4-6 string

#include <iostream>

#include <string>

using namespace std;

int main() {

char a[] = “维克托算法联盟”; //the end of the string will be a ‘\0’, which made it as the string for the system recognizing 

//the GBK UTF-8 can change the encode ways 

//this is the C style string

cout << sizeof(a) << endl;

cout << a << endl;

string b = “夜深人静看算法”;//this is C++ style string 

cout << b +”vito” << endl; // import the string class can add another string easily 

return 0;

}

//4-7 type bool

#include <iostream>

using namespace std;

// bool is true or flase

int main() {

bool flag1 = false;

bool flag2 = true;

cout << flag1 << endl << flag2 << endl;

cout << sizeof(bool) << endl;

flag1 = !flag1;

cout << flag1 << endl << flag2 << endl;

cout << sizeof(flag1) << endl;//bool’s size is 1

int flag3 = 0;

cout << sizeof(flag3) << endl; // int=byte, which size is 4

return 0;

}

//4-8 input

#include <iostream>

#include <string>

//i=input

//o = output

using namespace std;

int main() {

//1.int’s input

int a = 5;

cin >> a; // the right used to input into some variables

cout << “a turned to :” << a << endl;

//2.float’s input

double b = 5;

cin >> b; // the right used to input into some variables

cout << “b turned to :” << b << endl;

//3.char’s input

char c = 5;

cin >> c; // the right used to input into some variables

cout << “c turned to :” << c << endl;

//4.string’s input

string d = “”;

cin >> d; // the right used to input into some variables

cout << “d turned to :” << d << endl;

//5.bool’s input

bool e = false;

cin >> e; // the right used to input into some variables

cout << “e turned to :” << e << endl;

return 0;

//all the input must be legal

}

#include <iostream>

using namespace std;

int main()

// short 2字节     00       2 ^16   [-2 ^ 15 ~2 ^ 15 – 1]  [-32768~32767]

// int 4字节       0000     2 ^ 16  [-2 ^ 31 ~2 ^ 31 – 1] [-2147483648~2147483647]

// long 4字节 8字节 0000     2 ^ 16  [-2 ^ 31 ~2 ^ 31 – 1]

// long long 8字节 00000000  2 ^ 16 [-2 ^ 63 ~2 ^ 63 – 1]

//[l,r]

// range:r-l+1

//make it close to the range can save the space ,so watch out the range

{

    short a = 32768; // will be get out of the range,and turn to the loop’s start -32768

    int b = 2147483648;

    long c = 1;

    long long d = 1;

    cout << “a=” << a << endl;

    a = 32769;

    cout << “a2=” << a << endl; // show out -32767

    cout << “b=” << b << endl;

    cout << “c=” << c << endl;

    cout << “d=” << d << endl;

    return 0;

}

//new reserver symbol sizeof()

#include <iostream>

using namespace std;

int main()

{

    short a = 1;

    int b = 1;

    long c = 1;

    long long d = 1;

    cout << sizeof(short) << endl;

    cout << sizeof(int) << endl;

    cout << sizeof(long) << endl;

    cout << sizeof(long long) << endl;

    cout << sizeof(a) << endl;

    cout << sizeof(b) << endl;

    cout << sizeof(c) << endl;

    cout << sizeof(d) << endl;

    return 0;

}

#include <iostream>

#include <iomanip>

#include <cmath>

using namespace std;

int main()

#define eps 1e-7

// float 0000 4bytes

/// double 00000000 8bytes

// if you want to solve the question,must use double ,or you will miss the acuracy

// to judge the accuration of float, please make it minus in a small range

{

    float a = 13.1415926f;

    double b = 13.1415926;

    cout << setprecision(10) << a << endl;

    cout << setprecision(10) << b << endl;

    a = 13.1415926f;

    b = 13.141592611111111111;

    cout << setprecision(10) << a << endl;

    cout << setprecision(30) << b << endl; // if you make it out of range ,can still display the wrong number

    cout << sizeof(a) << endl;

    cout << sizeof(b) << endl;

    double c = 1.5e5; // 1.5*10^5

    cout << c << endl;

    double d = 1.5e-5; // 1.5*10^-5

    cout << d << endl;

    double x = 1.0 / 123123111123123123 * 123123111123123123; // when the float is large enough,must will have the error

    cout << x << endl;

    if (fabs(x – 1) < 0.00000001)

    {

        cout << “one two” << endl;

    }

    if (fabs(x – 1) < eps)

    {

        cout << “one two” << endl;

    }

    return 0;

}

#include <iostream>

using namespace std;

#define X “Vito写算法”

#define Y “Deep Night”

int main() {

cout <<X <<endl <<Y<<endl ;

//define constant can substitute sth

}

#include <iostream>

using namespace std;

#define X “Vito写算法”

#define Y “Deep Night”

#define Z 1+2

#define G (1+2)

const int x = 8;

int main() {

cout <<X <<endl <<Y<<endl ;

cout << Z*Z<<endl; //would be 5,cause 1+2*1+2=5

cout << G * G<< endl; // would be 9,cause you add the ()

//x = (x + 1); //if add up the const ,this x can’t be modify

//c++ is  upper and lower case sensitive 

cout << x << endl;

}

#include <iostream>

using namespace std;

int main(){

//int float;//it is wrong because you can’t use the reserve key as the symbol

int a = 5;

if (a == 6) {

return -1;

}

return -2;

}

#include <iostream>

using namespace std;

int main() {

int a12_ = 520;

//int 9b_ = 22; //number can’t be the start of the literal

int a = 5;

int A = 8;

cout << a << endl << A <<endl;

int appleCount = 0;

int chuangshijiejing = 0; //pinyin can be normal if you are in the chinese group

#include <iostream>

using namespace std;

int main() {

int a12_ = 520;

//int 9b_ = 22; //number can’t be the start of the literal

int a = 5;

int A = 8;

cout << a << endl << A <<endl;

int appleCount = 0;

int chuangshijiejing = 0; //pinyin can be normal if you are in the chinese group

//variety Literal of C++

/*1.case sensitive

2.can not be started with number

3.can not be the system reserve literal

4.you can use word,number,_ as the variety Literal*/

}

1. Leant how to install the environment 
2. The dream is to code a game for me
3. Found the reason of headache:fit the brain 
4. Not the copy&paste, if you write more, you remember more
5. Try to answer the question  by yourself, do not to ask other people the first time

#include <iostream>

using namespace std;

int main()

{

cout << “Vito Algorithm” << endl <<endl <<endl; //endl is change the line

return -12;

}

#include <iostream>

//using namespace std;

int main()

{

std::cout << “Vito Algorithm” << std::endl << std::endl << std::endl; //endl is change the line

// i can use std:: before the cout and endl, so that i don’t need to script namespace

//the namespace, which is used to divide the different codes that uses the same variety name 

/*

multiple notes

*/

return -12;

}

#include <iostream>

using namespace std;

int main()

{

//std::cout << “Vito Algorithm” << std::endl << std::endl << std::endl; //endl is change the line

//the definition of the variety:type name =origin value;

//please give the variaty a origin value, if you didn’t do it, you are making errors when you are cout

int a = 520;

int b;

cout << a << endl;

cout << b << endl;

return 0;

}