Loops

If we need to output something 10 times, we need to write that same thing again & again 10 times. Here Loops make things easier for us.

// without loop

cout << "Hello" <<endl;
cout << "Hello" <<endl;
cout << "Hello" <<endl;
......................
......................

// with loop

for (int i = 0; i < 10; i++) {
    cout << "Hello" << endl;
}

Loops can execute a block of code as long as a specified condition is met.
Loops are handy because they save time, reduce errors, and they make code more readable.
There are mainly two types of loops :

Entry Controlled Loops

The test condition is tested before entering the loop body.
for loop & while loop

Exit Controlled Loops

Test condition is tested or evaluated at the end of the loop body.
Therefore, the loop body will execute at least once, irrespective of whether the test condition is true or false
do-while loop

for loop

The for loop is generally used when the number of iterations is known in advance.

for (initialization; condition; update) {
    // code to be executed
}

for (int i = 0; i < 5; ++i) {
    // code to be executed 5 times
}

for (auto element : arr) {
    // code
}

For Loop Flow Chart :
For loop is a counter-controlled loop.
Usually for loop is written with counter. for(int i = 0; i < n; i++) here i is a counter
for loop can be written like this for(;;)

while loop

The while loop is generally used when the number of iterations is not known in advance, and it continues to execute as long as a specified condition is true.

initialization expression;
while (test_expression) {
    // statements
    update_expression;
}

int i = 0;
while (i < 5) {
    // code to be executed as long as i is less than 5
    ++i;
}

While & Do-While Loop Flow Chart :

do-while loop

The do-while loop is similar to the while loop, but in the do-while loop the condition is tested at the end of the loop body.

It always executes the code block at least once, even if the condition is initially false.

initialization expression;
do
{
    // statements
    update_expression;
} while (test_expression);

int i = 0;
do {
    // code to be executed at least once
    ++i;
} while (i < 5);

Range-based for loop / for-each loop

Range-based for loop has been added since C++ 11.

A convenient and concise way to iterate over elements in a range, such as an array, container, or any sequence of elements.

for ( range_declaration : range_expression ) {
    //  loop_statement
}

int arr[] = {1, 2, 3, 4, 5};
for (int value : arr) {
    cout << value << " ";
}

vector<int> vec = {1, 2, 3, 4, 5};
for (int value : vec) {
    cout << value << " ";
}

Break statement in loops

The break statement can also be used to jump out of a loop.

// This program jumps out of the loop when i is equal to 4:

for (int i = 0; i < 10; i++) {
    if (i == 4) {
        break;
    }
    cout << i << endl;
}

- break statement can apply in other loops as well.

Continue statement in loops

The continue statement breaks one iteration (in the loop) if a specified condition occurs, and continues with the next iteration in the loop.

for (int i = 0; i < 10; i++) {
    if (i == 4) {
        continue;
    }
    cout << i << endl;
}

continue statement can apply in other loops as well.