a. C ++ Tips

Based on the range for loop

double prices[5] = {4.99, 10.99, 6.87, 9.58, 11.49};
for(double x : prices)
    cout<<x<<endl;

Logical operator shorting

The &&expression on the left, if it is determined false, it is not determined expression / execution right

const pointers and pointers to const

*Direct contact with the name of the pointer is a pointer to a const

int i = 10;
int j = 10;
// 变量值不可修改
const int ci = i;
ci = 1;    //error
// 1. 指针指向的内存不可修改
const int* pi1 = &i;
*pi1 = 1;   // error
pi1 = &j;
// 2. 等价于 1
int const* pi2 = &i;
*pi2 = 1;   // error
pi2 = &j;
// 3. 指针不可修改
int* const pi3 = &i;
*pi3 = 1;
pi3 = &j;   // error
// 4. 没有这种语法
const* int pi4 = &i;    // error
// const int*类型的值不能用于初始化int*变量
int* pi4 = pi1;    // error

Command-line arguments (imitation C)

Code:

// option.exe
#include<stdio.h>

int main(int argc, char* argv[])
{
    printf("%d arguments in all.\n", argc);
    for(int i = 0; i < argc; i++)
        printf("%d: %s\n", i+1, argv[i]);
    return 0;
}

Command line:

...>g++ option.cpp -o option.exe

...>option -i infile -o outfile

Command line output:

5 arguments in all.
1: option
2: -i
3: infile
4: -o
5: outfile

The first parameter is the path to the program, which is the program name on the command line (or full path)

C ++ will automatically spliced ​​spaced blank / continuous string

It can be written:

cout << "Hello World!\n"
        "Still water runs deep.\n"
        "Can you can a can like a canner can a can?";

Generating a pseudo-random number

You need to include <ctime>and <random>two headers.

#include <Windows.h>    // for Sleep()
#include <iostream>
#include <ctime>
#include <random>
#pragma (lib, "Kernel32.lib")
using namespace std;

int main()
{
    for(int i = 0; i < 10; ++i)
    {
        srand(time(0));
        cout << "# " << i+1 << " : " << rand() << endl;
        Sleep(1000);
    }

    return 0;
}

# 1 : 16695
# 2 : 16699
# 3 : 16702
# 4 : 16705
# 5 : 16708
# 6 : 16712
# 7 : 16715
# 8 : 16718
# 9 : 16721
# 10 : 16725

Noting the gap between these "random number" is not great. This is because rand()according to srand()generate "random number" value is passed, if not Sleep(1000), then even the same ten numbers will appear.