24. C pointers and arrays. C pointers and arrays.md

C Pointers and Arrays

Video Link: https://youtu.be/LscgaBzlGdE
Tutorial Link: https://www.programiz.com/c-programming/c-pointers-arrays

C Pointers and Array

##include <stdio.h>

int main() {

  int numbers[5] = {1, 3, 5, 7, 9};

  for (int i = 0; i < 5; ++i) {
    printf("%d = %p\n", numbers[i], &numbers[i]);
  }
  
  return 0;
}

Output

1 = 0x7ffce02ace30
3 = 0x7ffce02ace34
5 = 0x7ffce02ace38
7 = 0x7ffce02ace3c
9 = 0x7ffce02ace40

Using name of the array to print the address

#include <stdio.h>

int main() {

  int numbers[5] = {1, 3, 5, 7, 9};

  for (int i = 0; i < 5; ++i) {
    printf("%d = %p\n", numbers[i], numbers+i);
  }

  return 0;
}

Output

1 = 0x7fff55603c30
3 = 0x7fff55603c34
5 = 0x7fff55603c38
7 = 0x7fff55603c3c
9 = 0x7fff55603c40

Access array elements using pointer

#include <stdio.h>

int main() {

  int numbers[5] = {1, 3, 5, 7, 9};

  for (int i = 0; i < 5; ++i) {
    printf("%d = %p\n", *(numbers+i), numbers+i);
  }

  return 0;
}

Output

1 = 0x7ffd2398cc80
3 = 0x7ffd2398cc84
5 = 0x7ffd2398cc88
7 = 0x7ffd2398cc8c
9 = 0x7ffd2398cc90

Change array elements using pointers

#include <stdio.h>

int main() {

  int numbers[5] = {1, 3, 5, 7, 9};

  *numbers = 2;
  *(numbers+4) = 11;

  printf("First Element: %d\n", *numbers);
  printf("Last Element: %d", *(numbers+4));

  return 0;
}

Output

First Element: 2
Last Element: 11

---

Programming Task

Create a program to find the largest element of an array using pointers.

int arr[] = {34, 12, 21, 54, 48};

• assign the first element of the array to a largest variable using pointer
  int largest = *arr

• Run a for loop to access each element of the array.

• Compare largest with each array element using pointer
  largest < *(arr + i)

• If the largest variable is smaller than a element, assign the array value to largest
  largest = *(arr + i)

Solution

#include <stdio.h>

int main() {
    int arr[5] = {34, 12, 21, 54, 48};
    
    int largest = *arr;
    
    for(int i = 1; i < 5; i++) {
        if(largest < *(arr + i)) {
            largest = *(arr + i);
        }
    }
     printf("The largest number is: %d", largest);
    
    return 0;
}

Output

The largest number is: 54

---

Programiz Quiz

Q. In an array, int ages[5], what does ages represent?

Options:

1. ages[4]
2. ages[0]
3. &ages[4]
4. &ages[0]

Answer: 4