Loop Constructs

#include <stdio.h>

int main() {
    // for loop
    for (int i = 0; i < 10; i++) {
        printf("%d ", i);  // 0 1 2 3 4 5 6 7 8 9
    }
    printf("\n");

    // while loop (condition checked first)
    int count = 0;
    while (count < 5) {
        printf("Count: %d\n", count);
        count++;
    }

    // do-while (runs at least once)
    int input;
    do {
        printf("Enter positive number: ");
        scanf("%d", &input);
    } while (input <= 0);  // Keeps asking until valid

    // break: exit loop early
    for (int i = 0; i < 100; i++) {
        if (i == 42) break;  // Exit at 42
        printf("%d ", i);
    }

    // continue: skip to next iteration
    for (int i = 0; i < 10; i++) {
        if (i % 2 == 0) continue;  // Skip even numbers
        printf("%d ", i);  // 1 3 5 7 9
    }

    // Nested loops: multiplication table
    for (int row = 1; row <= 5; row++) {
        for (int col = 1; col <= 5; col++) {
            printf("%4d", row * col);
        }
        printf("\n");
    }

    // Practical: find prime numbers
    for (int num = 2; num <= 50; num++) {
        int isPrime = 1;
        for (int div = 2; div * div <= num; div++) {
            if (num % div == 0) {
                isPrime = 0;
                break;
            }
        }
        if (isPrime) printf("%d ", num);
    }

    return 0;
}