looping

for loop

// for loop
// for (initialization; condition; increment)
//     statement;
// example
int i = 0;
for (i = 1; i <= 5; ++i)
    cout << i << endl;
// i only visible in the loop!:
for (int i = 1; i <= 5; ++i){
    cout << i << endl;
}
// when using arrays i cant be at maximum the size of the array -1!
// with comma operator
for (int i = 1, j = 1; i <= 5; ++i, j++){
    cout << i << endl;
    cout << j << endl;
}

range-based for loop

// range-based for loop (Cpp11 or newer, extension!)

// example 1
for (var_type var_name: sequence)
      statement; // can use var_name

// example 2
for (var_type var_name: sequence) {
     statements; // can use var_name
}

// // example 3
int scores[] = {10, 20, 30};

for (int score : scores)
    cout << score << endl;

for (auto score : scores)
    cout << score << endl;

// example 4
vector<double> temps = {23.1, 77.1, 90.3, 93.2};
double average_temp = 0;
double running_sum = 0;

for (auto temp: temps)
    running_sum += temp;

average_temp = running_sum / temps.size();

while loop

// called pre-test loop
// example 1
i = 1;
while (i <= 5) {
    cout << i << endl;
    ++i; //important!
}
// example 2, get all even numbers from 1 to 10
i = 1;
while (i <= 10) {
    if (i % 2 == 0)
    cout << i << endl;
    ++i;
}
// example 3
int scores_2[] = {100, 90, 80};
i = 0;
while (i < 3){
    cout << scores_2[i] << endl;
    ++i;
}

// with boolean flag
// example 4 - input validation - boolean flag
bool done (false);
int number = 0;

while (!done){
    cout << "Enter an integer between 1 and 5: ";
    cin >> number;
    if (number <=1 || number >= 5)
    cout << "Out of range, try again" << endl;
    else {
        cout << "Thanks!" << endl;
        done = true;
    }
}

do-while loop

// post-test-loop
// do {
//     statements;
// } while (expression);
// example 1
int number2 = 0;
do {
    cout << "Enter an integer between 1 and 5: ";
    cin >> number2;
} while (number2 <= 1 || number2 >=5);

cout << "Thanks" << endl;

// example 2
char selection = ' ';
do {
    double width = 0, height = 0;
    cout << "Enter width and height separated by a space: ";
    cin >> width >> height;

    double area = {width * height};
    cout << "The area is " << area << endl;

    cout << "Calculate another? (Y/N): ";
    cin >> selection;
} while (selection == 'Y' || selection == 'y');

cout << "Thanks!" << endl;

continue and break statements

// continue and break statements in the loop
// break - break out from loop completely
// continue - skip rest of the loop/stopping iteration and starting directly into next iteration
// example

vector<int>values = {1,2,-1,3,-1,-99,7,8,10};
for (auto val: values) {
   if (val == -99)
        break;
    else if (val == -1)      
        continue;
	  else
				cout << val << endl;
}

nested loops

// example - inner loop loops faster
for (int outer_val = 1; outer_val <= 2; ++outer_val)
    for (int inner_val = 1; inner_val <= 3; ++inner_val)
        cout << outer_val << ", " << inner_val << endl;

// example 2
int grid[5][3] = {};
for (int row = 0; row < 5; ++row ) {
    for (int col = 0; col < 3; ++col ) {
        grid[row][col] = 1000;
    }
}