loops.md

Loops

Loops are a way to repeat code multiple times without copying it.

FOR loop

A for loop repeats a section of code a limited amount of times.

Example:

// we declare a variable i and set it to 1, the loop will then continue as long as the condition in the middle is true, in
// this case i <= 10, and the statement at the end will be executed at the end of each loop, in this case incrementing i by 1
for (int i = 1; i <= 10; i++) {
	printf("loop %d\n", i); // -> loop 1
				// -> loop 2
				// -> loop 3
				// -> loop 4
				// -> loop 5
				// -> loop 6
				// -> loop 7
				// -> loop 8
				// -> loop 9
				// -> loop 10
}

WHILE loop

Standard while

A while loop repeats a section of code as long as a condition is true.

Example:

char name[25];

printf("What is your name? ");
fgets(name, 25, stdin);
name[strlen(name) - 1] = '\0';

while (strlen(name) == 0) { // the loop will continue as long as the user hasn't given an answer
	printf("You did not enter your name.\n");
	printf("What is your name? ");
	fgets(name, 25, stdin);
	name[strlen(name) - 1] = '\0';
}

do while

A do while loop is like a while loop, except it executes the code inside of it before checking the condition.

Example:

int n = 0;
int sum;

do {
	printf("Enter a number above 0: ");
	scanf("%d", &n);
	if (n > 0) {
		sum += n;
	}
} while (n > 0); // the code above will run once, then check the condition and continue running if it is true

break and continue

The continue statement skips the rest of the code and forces the next iteration of the loop. The break statement exits the loop (or the switch).

Example:

for (int i = 1; i <= 20; i++) {
	if (i == 13) { 	   // skip this iteration if i == 13
		continue;
	}
	printf("%d\n", i); // -> 1
			   // -> 2
			   // -> 3
			   // -> 4
			   // -> 5
			   // -> 6
			   // -> 7
			   // -> 8
			   // -> 9
			   // -> 10
			   // -> 11
			   // -> 12
			   // -> 14
			   // -> 15
			   // -> 16
			   // -> 17
			   // -> 18
			   // -> 19
			   // -> 20
}

for (int i = 1; i <= 20; i++) {
	if (i == 13) { 	   // exit the loop if i == 13
		break;
	}
	printf("%d\n", i); // -> 1
			   // -> 2
			   // -> 3
			   // -> 4
			   // -> 5
			   // -> 6
			   // -> 7
			   // -> 8
			   // -> 9
			   // -> 10
			   // -> 11
			   // -> 12
}