Loop

while (and do while) loop

C

src/c/basics/04-while-loop.c

#include <stdio.h>

int main()
{
    int i = 1, i2 = 0;

    while (i < 10)
    {
        i2 = i * i;
        printf("%d\t%d\n", i, i2);
        i++;
    }

    // do while loop
    printf("\nExample of do-while loop:\n");
    i = 1;
    do
    {
        i2 = i * i;
        printf("%d\t%d\n", i, i2);
        i++;
    } while (i < 10);

    return 0;
}

C++

src/cpp/basics/04-while-loop.cpp

#include <iostream>
using namespace std;

int main()
{
    int i = 1;

    while (i <= 10)
    {
        cout << i << "\t" << i * i << endl;
        ++i;
    }

    cout << endl;

    // do while loop
    i = 1;
    do
    {
        cout << i << "\t" << i * i * i << endl;
        ++i;
    } while (i <= 10);

    return 0;
}

for loop

C

src/c/basics/04-for-loop.c

#include <stdio.h>

int main()
{
    int i = 10;
    int i2 = 0;

    for (i = 1; i < 10; i++)
    {
        i2 = i * i;
        printf("%d\t%d\n", i, i2);
    }
    
    return 0;
}

C++

src/cpp/basics/04-for-loop.cpp

#include <iostream>
using namespace std;

int main()
{
    int i;
    cout << "For loop variant 1:\n";
    for (i = 0; i < 5; i++)
    {
        cout << i << endl;
    }

    int j = 0;
    cout << "\nFor loop variant 2:\n";
    for (; j < 5; j++) // since j is already initialized, loop condition can
                       // start with null statement
    {
        cout << j << endl;
    }

    cout << "\nFor loop variant 3:\n";
    for (int k = 0; k < 5; k++) // loop variable can be locally declared
    {
        cout << k << endl;
    }

    int size = 5;
    int arr[5] = {1, 2, 3, 4, 5};
    int sum = 0;
    for (int i = 0; i < size;)
    {
        sum += arr[i++]; // post increment i after accessing array element
    }

    cout << "sum = " << sum << endl;

    return 0;
}

Break and continue

src/cpp/basics/04-break-continue.cpp

#include <iostream>
using namespace std;

int main()
{
    int i = 0;

    for (;;) // forever for loop
    {
        i++;

        if (i > 10)
            break;

        if ((i % 2) == 0)
        {
            continue; // jumps to the loop beginning
        }
        else
        {
            cout << i << endl; // print odd numbers
        }
    }

    return 0;
}