Basic C++ Example Code

0.2-0_macOS_tasks.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "Open Terminal",
            "type": "shell",
            "command": "osascript -e 'tell application \"Terminal\"\ndo script \"echo hello\"\nend tell'",
            "problemMatcher": []
        },
        {
            "type": "shell",
            "label": "clang++ build active file",
            "command": "/usr/bin/clang++",
            "args": [
                "-std=c++17",
                "-stdlib=libc++",
                "-g",
                "${file}",
                "-o",
                "${fileDirname}/${fileBasenameNoExtension}"
            ],
            "options": {
                "cwd": "${workspaceFolder}"
            },
            "problemMatcher": [
                "$gcc"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            }
        }
    ]
}

0.2-1_macOS_launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "clang++ - Build and debug active file",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}/${fileBasenameNoExtension}",
            "args": [],
            "stopAtEntry": true,
            "cwd": "${workspaceFolder}",
            "environment": [],
            "externalConsole": false,
            "MIMode": "lldb",
            "preLaunchTask": "clang++ build active file"
        }
    ]
}

1-0_hello_world.cpp

#include <iostream>

using namespace std;

int main()
{
    cout << "hello, world";
    return 0;
}

1-1_newline.cpp

#include <iostream>

using namespace std;

int main()
{
    cout << "hello, world\nhi, nevikw39\n";
    return 0;
}

1-2_output.cpp

#include <iostream>

using namespace std;

int main()
{
    cout << "87*69 = " << 87 * 69 << "\n9487*426 - 89*64 + 87*69 = " << 9487 * 426 - 89 * 64 + 87 * 69 << '\n';
    return 0;
}

1.1-0_int.cpp

#include <iostream>

using namespace std;

int main()
{
    int n = 87 * 69;
    cout << "87*69 = " << n << "\n9487*426 - 89*64 + 87*69 = " << 9487 * 426 - 89 * 64 + n << '\n';
    return 0;
}

1.1-1_input.cpp

#include <iostream>

using namespace std;

int main()
{
    int n;
    cout << "Please input an integer and press Enter: ";
    cin >> n;
    cout << "You inputed " << n << "!\n";
    return 0;
}

1.1-2_div_n_mod.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cout << "Please input two integers a and b: ";
    cin >> a >> b;
    cout << "a/b = " << a / b << "\n"
         << "a%b = " << a % b << "\n";
    return 0;
}

1.2-0_add.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    cout << a + b << "\n";
    return 0;
}

2-0_if.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cout << "Please input two integers a and b: ";
    cin >> a >> b;
    if (b != 0)
        cout << "a/b = " << a / b << "\n"
             << "a%b = " << a % b << "\n";
    return 0;
}

2-1_if_else.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cout << "Please input two integers a and b: ";
    cin >> a >> b;
    if (b)
        cout << "a/b = " << a / b << "\n"
             << "a%b = " << a % b << "\n";
    else
        cout << "Divisor cannot be 0!\n";
    return 0;
}

2-2_switch.cpp

#include <iostream>

using namespace std;

int main()
{
    int day;
    cin >> day;
    switch (day)
    {
    case 2:
         cout << "SUKIYA\n";
         break;
    case 3:
         cout << "那個那個飯\n";
         break;
    case 4:
         cout << "癡麵\n";
         break;
    case 0:
    case 7:
         cout << "Burger King\n";
         break;
    default:
        cout << "No cram school today.\n";
    }
    return 0;
}

2-3_g_c032.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    if (a + b >= 120)
        cout << "2\n";
    else if (a >= 60 || b >= 60)
        cout << "1\n";
    else
        cout << "0\n";
}

2-4_g_c032_arithmetic.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    cout << (a >= 60) + (b >= 60) << '\n';
}

2-5_g_c014.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b, d;
    scanf("%d%d", &a, &b);
    if (b > a)
        d = b - a;
    else
        d = a - b;
    if (d > 200)
        cout << b * 3 << '\n';
    else if (b > 20)
        cout << b * 4 << '\n';
    else
        cout << "0\n";
    return 0;
}

2-6_g_c014_arithmetic.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b;
    cin >> a >> b;
    b = abs(a - b);
    cout << (max(b - 20, 0) << 2) - max(b - 200, 0) << '\n';
    return 0;
}

2.1-0_while_rand.cpp

#include <iostream>
#include <random>

using namespace std;

int main()
{
    default_random_engine random(random_device{}());
    uniform_int_distribution<int> dice(1, 6);
    int val = dice(random), n = 0;
    while (n != val)
    {
        cout << "Please guess the lucky number your dice is: ";
        cin >> n;
    }
    cout << "Congratulate!! You got it. The lucky number is " << val << '\n';
    return 0;
}

2.1-1_while.cpp

#include <iostream>

using namespace std;

int main()
{
    int n;
    cin >> n;
    while (n--)
        cout << "hello, world\n";
    return 0;
}

2.1-2_do_while_rand.cpp

#include <iostream>
#include <random>

using namespace std;

int main()
{
    default_random_engine random(random_device{}());
    uniform_int_distribution<int> dice(1, 6);
    int val = dice(random), n;
    do
    {
        cout << "Please guess the lucky number your dice is: ";
        cin >> n;
    } while (n != val);
    cout << "Congratulate!! You got it. The lucky number is " << val << '\n';
    return 0;
}

2.1-3_for.cpp

#include <iostream>

using namespace std;

int main()
{
    int n;
    cin >> n;
    for (int i = 0; i < n; i++)
        cout << i << ". hello, world\n";
    return 0;
}

2.1-4_break.cpp

#include <iostream>

using namespace std;

int main()
{
    int n, k;
    cin >> n >> k;
    for (int i = 0; i < n; i++)
    {
        int a;
        cin >> a;
        if (a == k)
        {
            cout << i << '\n';
            break;
        }
    }
    return 0;
}

2.1-5_continue.cpp

#include <iostream>

using namespace std;

int main()
{
    for (int i = 0; i < 100; i++)
    {
        if (i == 64)
        {
            cout << "敏感词汇已屏蔽\n";
            continue;
        }
        cout << i << '\n';
    }
    return 0;
}

2.1-6_nested_loop.cpp

#include <iostream>
#include <iomanip>

using namespace std;

int main()
{
    for (int i = 1; i < 10; i++)
    {
        for (int j = 1; j < 10; j++)
            cout << i << '*' << j << '=' << setw(2) << i * j << ' ';
        cout << '\n';
    }
    return 0;
}

2.1-7_g_c046.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b, n;
    cin >> a >> b >> n;
    cout << a / b << '.';
    a %= b;
    while (n--)
    {
        a *= 10;
        cout << a / b;
        a %= b;
    }
    return 0;
}

2.1-8_g_c004.cpp

#include <iostream>

using namespace std;

int main()
{
    int n = 0;
    for (int i = 1; i < 8; i++)
    {
        char c;
        cin >> c;
        n += (c - '0') * i;
    }
    cout << (10 - n % 10) % 10 << '\n';
    return 0;
}

2.1-8_g_c040.cpp

#include <iostream>

using namespace std;

int main()
{
    int a, b, m, n;
    cin >> a >> b;
    m = a;
    n = b;
    while (a % b)
    {
        cout << a << '%' << b << '=' << a % b << '\n';
        int t = b;
        b = a % b;
        a = t;
    }
    cout << a << '%' << b << '=' << a % b << '\n'
         << "GCD(" << m << ',' << n << ")=" << n << '\n';
    return 0;
}

2.2-0_goto.cpp

#include <iostream>

using namespace std;

int main()
{
    int n, m, k;
    cin >> n >> m >> k;
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
        {
            int a;
            cin >> a;
            if (a == k)
            {
                cout << i << ' ' << j << '\n';
                goto end;
            }
        }
end:
    return 0;
}

3-0_pointer.cpp

#include <iostream>

using namespace std;

int main()
{
    int n = 87, *ptr = &n;
    cout << "n = " << n << ", &n = " << &n << '\n'
         << "ptr = " << ptr << ", *ptr = " << *ptr << '\n';
    n = 69;
    cout << "n = " << n << ", &n = " << &n << '\n'
         << "ptr = " << ptr << ", *ptr = " << *ptr << '\n';
    *ptr = 89;
    cout << "n = " << n << ", &n = " << &n << '\n'
         << "ptr = " << ptr << ", *ptr = " << *ptr << '\n';
    return 0;
}

3-1_const_pointers.cpp

#include <iostream>

using namespace std;

int main()
{
    const int ca = 69, cb = 777, *ptr0 = &ca;
    cout << "ptr0 = " << ptr0 << ", *ptr0 = " << *ptr0 << '\n';
    ptr0 = &cb;
    cout << "ptr0 = " << ptr0 << ", *ptr0 = " << *ptr0 << '\n';
    // *ptr0 is read-only constant.
    /*
    *ptr0 = 9487;
    cout << "ptr0 = " << ptr0 << ", *ptr0 = " << *ptr0 << '\n';
     */
    int na = 87, nb = 666, *const ptr1 = &na;
    cout << "ptr1 = " << ptr1 << ", *ptr1 = " << *ptr1 << '\n';
    // ptr1 is read-only constant.
    /*
    ptr1 = &nb;
    cout << "ptr1 = " << ptr1 << ", *ptr1 = " << *ptr1 << '\n';
     */
    *ptr1 = nb;
    cout << "ptr1 = " << ptr1 << ", *ptr1 = " << *ptr1 << '\n';
    const int *const ptr2 = &ca;
    cout << "ptr2 = " << ptr2 << ", *ptr2 = " << *ptr2 << '\n';
    // ptr2 is read-only constant.
    /*
    ptr2 = &cb;
    cout << "ptr2 = " << ptr2 << ", *ptr2 = " << *ptr2 << '\n';
     */
    // *ptr2 is read-only constant.
    /*
    *ptr2 = 9487;
    cout << "ptr2 = " << ptr2 << ", *ptr2 = " << *ptr2 << '\n';
     */
    return 0;
}

3.1-0_g_c041.cpp

#include <iostream> 

using namespace std;  

int main()  
{   
    int n, avg = 0, r = 0;  
    cin >> n;  
    int arr[n];  
    for (int i = 0; i < n; i++)  
    {  
        cin >> arr[i];  
        avg += arr[i];  
    }  
    avg /= n;  
    for (int i = 0; i < n; i++)  
        r += abs(arr[i] - avg);  
    cout << r / 2 << '\n';  
    return 0;  
}  

3.1-1_array.cpp

#include <iostream>

using namespace std;

int main()
{
    int arr[3];
    arr[0] = 9;
    arr[1] = 8;
    arr[2] = 7;
    cout << arr + 0 << ' ' << *(arr + 0) << '\n'
         << arr + 1 << ' ' << *(arr + 1) << '\n'
         << arr + 2 << ' ' << *(arr + 2) << '\n';
    return 0;
}

3.1-2_traversal.cpp

#include <iostream>

using namespace std;

int main()
{
    int arr[10];
    for (int i = 0; i < 10; i++)
        cin >> arr[i];
    for (int i = 0; i < 10; i++)
        cout << arr[i] << '\n';
    return 0;
}

3.1-3_traversal_pointer.cpp

#include <iostream>

using namespace std;

int main()
{
    int arr[10];
    for (int *ptr = arr; ptr < arr + 10; ptr++)
        cin >> *ptr;
    for (const int *ptr = arr; ptr < arr + 10; ptr++)
        cout << *ptr << '\n';
    return 0;
}

3.1-4_traversal_ranged_for.cpp

#include <iostream>

using namespace std;

int main()
{
    int arr[10];
    for (int &i : arr)
        cin >> i;
    for (const int &i : arr)
        cout << i << '\n';
    return 0;
}

3.1-5_traversal_stream_iterator.cpp

#include <iostream>
#include <algorithm>
#include <iterator>

using namespace std;

int main()
{
    int arr[10];
    copy_n(istream_iterator<int>(cin), 10, arr);
    copy(arr, arr + 10, ostream_iterator<int>(cout, "\n"));
    return 0;
}

3.1-6_vector.cpp

#include <iostream>
#include <vector>
#include <iterator>

using namespace std;

int main()
{
    vector<int> v0(5), v1(5, 87), v2 = {4, 3, 2, 1, 0}, v3 = v2;
    cout << "v0:\n";
    for (int i = 0; i < 5; i++)
        cout << '\t' << v0[i] << '\n';
    cout << "v1:\n";
    for (auto itr = v1.begin(); itr < v1.end(); itr++) // Here, `auto` would be `vector<int>::iterator`
        cout << '\t' << *itr << '\n';
    cout << "v2:\n";
    for (const int &i : v2)
        cout << '\t' << i << '\n';
    cout << "v3:\n\t";
    copy(v3.begin(), v3.end(), ostream_iterator<int>(cout, "\n\t"));
    return 0;
}