Nested loops over Arrays in C programming refer to having one loop inside another loop.
This allows us to execute a set of instructions multiple times, where each iteration of the outer loop triggers a complete set of iterations of the inner loop.
Nested loops are commonly used for tasks such as iterating through multi-dimensional arrays or generating patterns.
#include <stdio.h>
int main() {
int i, j;
// Outer loop for rows
for (i = 1; i <= 3; i++) {
// Inner loop for columns
for (j = 1; j <= 3; j++) {
printf("%4d", i * j); // Print the product of row and column
}
printf("\n"); // Move to the next line after completing each row
}
return 0;
}
1 2 3 2 4 6 3 6 9
the outer loop (for (i = 1; i <= 3; i++)) iterates through the rows, and the inner loop (for (j = 1; j <= 3; j++)) iterates through the columns.
Each iteration of the outer loop triggers 3 iterations of the inner loop, resulting in a complete row of the multiplication table being printed for each value of i.
#include <stdio.h>
int main() {
for (int i = 2; i <= 5; i+=2) { // Outer Loop
for (int j = 1; j <= 10; j++) { // Inner Loop
printf("%d * %d = %d\n", i, j, i * j);
}
printf("\n");
}
return 0;
}
Note: Above code prints the table of even numbers from 2 to 5.
Our Outer Loop starts executing from 2, and the inner loop iterates from 1 to 10. It will table of `2` and increment the outer loop value of `i` by 2.
Now, the Outer Loop `i` value is 4, it will skip iteration for value `i=3` because we have increment `i` by 2 in Outer Loop.
Next Iteration will print a table of `4` and increment the outer loop value of `i` by 2. Now, the outer loop `i` value is 6.
The next Iteration takes place and it will check the `6 < 5` condition will not verify and it comes out from the outer loop and starts executing the rest of the code after the loop.
2 * 1 = 2 2 * 2 = 4 2 * 3 = 6 2 * 4 = 8 2 * 5 = 10 2 * 6 = 12 2 * 7 = 14 2 * 8 = 16 2 * 9 = 18 2 * 10 = 20 4 * 1 = 4 4 * 2 = 8 4 * 3 = 12 4 * 4 = 16 4 * 5 = 20 4 * 6 = 24 4 * 7 = 28 4 * 8 = 32 4 * 9 = 36 4 * 10 = 40
Note: Above code finds and prints all prime numbers up to a given number (20 in this example).
#include <stdio.h>
#include <stdbool.h>
int main() {
int n = 20;
bool isPrime;
for (int i = 2; i <= n; i++) {
isPrime = true;
for (int j = 2; j <= i / 2; j++) {
if (i % j == 0) {
isPrime = false;
break;
}
}
if (isPrime)
printf("%d ", i);
}
return 0;
}
2 3 5 7 11 13 17 19 // Prime Number
They are commonly used in various scenarios where repetitive tasks need to be performed multiple times, often with patterns or iterating through data structures like arrays.