Arrays in Data Structures and Algorithms

An array is a collection of items stored at contiguous memory locations. It is a data structure that stores a fixed-size sequential collection of elements of the same type. An array is used to store a collection of data, but it is often more useful to think of an array as a collection of variables of the same type.

Visualizations of Arrays in Data Structures and Algorithms (DSA)

Speed:

Lowest value of [] :  

Why are Arrays important?

Arrays are important because they allow us to store multiple items of the same type in a single variable. They are used to store data in a structured way, and they are used in many algorithms and data structures.

How to declare an Array?

An array can be declared in various programming languages using the following syntax:

JavaScipt

Written by @Ajay-Dhangar

// Declare an array in JavaScript
let arr = [1, 2, 3, 4, 5];

Java

Written by @Ajay-Dhangar

// Declare an array in Java
int[] arr = {1, 2, 3, 4, 5};

Python

Written by @Ajay-Dhangar

# Declare an array in Python
arr = [1, 2, 3, 4, 5]

C

Written by @Ajay-Dhangar

// Declare an array in C
int arr[] = {1, 2, 3, 4, 5};

C++

Written by @Ajay-Dhangar

// Declare an array in C++
int arr[] = {1, 2, 3, 4, 5};

TypeScript

Written by @Ajay-Dhangar

// Declare an array in TypeScript
let arr: number[] = [1, 2, 3, 4, 5];

How to access an Array?

An array can be accessed using the index of the element. The index of the first element is 0, the index of the second element is 1, and so on.

JavaScipt

Written by @Ajay-Dhangar

// Access an array in JavaScript
let arr = [1, 2, 3, 4, 5];
console.log(arr[0]); // 1
console.log(arr[1]); // 2
console.log(arr[2]); // 3
console.log(arr[3]); // 4
console.log(arr[4]); // 5

Java

Written by @Ajay-Dhangar

// Access an array in Java
int[] arr = {1, 2, 3, 4, 5};
System.out.println(arr[0]); // 1
System.out.println(arr[1]); // 2
System.out.println(arr[2]); // 3
System.out.println(arr[3]); // 4
System.out.println(arr[4]); // 5

Python

Written by @Ajay-Dhangar

# Access an array in Python
arr = [1, 2, 3, 4, 5]
print(arr[0]) # 1
print(arr[1]) # 2
print(arr[2]) # 3
print(arr[3]) # 4
print(arr[4]) # 5

C

Written by @Ajay-Dhangar

// Access an array in C
int arr[] = {1, 2, 3, 4, 5};
printf("%d\n", arr[0]); // 1
printf("%d\n", arr[1]); // 2
printf("%d\n", arr[2]); // 3
printf("%d\n", arr[3]); // 4
printf("%d\n", arr[4]); // 5

C++

Written by @Ajay-Dhangar

// Access an array in C++
int arr[] = {1, 2, 3, 4, 5};
cout << arr[0] << endl; // 1
cout << arr[1] << endl; // 2
cout << arr[2] << endl; // 3
cout << arr[3] << endl; // 4
cout << arr[4] << endl; // 5

TypeScript

Written by @Ajay-Dhangar

// Access an array in TypeScript
let arr: number[] = [1, 2, 3, 4, 5];
console.log(arr[0]); // 1
console.log(arr[1]); // 2
console.log(arr[2]); // 3
console.log(arr[3]); // 4
console.log(arr[4]); // 5

How to update an Array?

An array can be updated by assigning a new value to the index of the element.

JavaScipt

Written by @Ajay-Dhangar

// Update an array in JavaScript
let arr = [1, 2, 3, 4, 5];
arr[0] = 10;
console.log(arr); // [10, 2, 3, 4, 5]

Java

Written by @Ajay-Dhangar

// Update an array in Java
int[] arr = {1, 2, 3, 4, 5};
arr[0] = 10;
System.out.println(Arrays.toString(arr)); // [10, 2, 3, 4, 5]

Python

Written by @Ajay-Dhangar

# Update an array in Python
arr = [1, 2, 3, 4, 5]
arr[0] = 10
print(arr) # [10, 2, 3, 4, 5]

C

Written by @Ajay-Dhangar

// Update an array in C
int arr[] = {1, 2, 3, 4, 5};
arr[0] = 10;
for (int i = 0; i < 5; i++) {
    printf("%d ", arr[i]);
}
// 10 2 3 4 5

C++

Written by @Ajay-Dhangar

// Update an array in C++
int arr[] = {1, 2, 3, 4, 5};
arr[0] = 10;
for (int i = 0; i < 5; i++) {
    cout << arr[i] << " ";
}
// 10 2 3 4 5

TypeScript

Written by @Ajay-Dhangar

// Update an array in TypeScript
let arr: number[] = [1, 2, 3, 4, 5];
arr[0] = 10;
console.log(arr); // [10, 2, 3, 4, 5]

How to find the length of an Array?

The length of an array can be found using the length property.

JavaScipt

Written by @Ajay-Dhangar

// Find the length of an array in JavaScript
let arr = [1, 2, 3, 4, 5];
console.log(arr.length); // 5

Java

Written by @Ajay-Dhangar

// Find the length of an array in Java
int[] arr = {1, 2, 3, 4, 5};
System.out.println(arr.length); // 5

Python

Written by @Ajay-Dhangar

# Find the length of an array in Python
arr = [1, 2, 3, 4, 5]
print(len(arr)) # 5

C

Written by @Ajay-Dhangar

// Find the length of an array in C
int arr[] = {1, 2, 3, 4, 5};
int length = sizeof(arr) // sizeof(arr[0]);
printf("%d\n", length); // 5

C++

Written by @Ajay-Dhangar

// Find the length of an array in C++
int arr[] = {1, 2, 3, 4, 5};
int length = sizeof(arr) // sizeof(arr[0]);
cout << length << endl; // 5

TypeScript

Written by @Ajay-Dhangar

// Find the length of an array in TypeScript
let arr: number[] = [1, 2, 3, 4, 5];
console.log(arr.length); // 5

How to iterate through an Array?

An array can be iterated using a loop such as for loop, while loop, or for...of loop.

JavaScipt

Written by @Ajay-Dhangar

// Iterate through an array in JavaScript
let arr = [1, 2, 3, 4, 5];
for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}
// 1
// 2
// 3
// 4
// 5

Java

Written by @Ajay-Dhangar

// Iterate through an array in Java
int[] arr = {1, 2, 3, 4, 5};
for (int i = 0; i < arr.length; i++) {
    System.out.println(arr[i]);
}
// 1
// 2
// 3
// 4
// 5

Python

Written by @Ajay-Dhangar

# Iterate through an array in Python
arr = [1, 2, 3, 4, 5]
for i in arr:
    print(i)
# 1
# 2
# 3
# 4
# 5

C

Written by @Ajay-Dhangar

// Iterate through an array in C
int arr[] = {1, 2, 3, 4, 5};
for (int i = 0; i < 5; i++) {
    printf("%d\n", arr[i]);
}
// 1
// 2
// 3
// 4
// 5

C++

Written by @Ajay-Dhangar

// Iterate through an array in C++
int arr[] = {1, 2, 3, 4, 5};
  for (int i = 0; i < 5; i++) {
      cout << arr[i] << endl;
  }
  // 1
  // 2
  // 3
  // 4
  // 5

TypeScript

Written by @Ajay-Dhangar

// Iterate through an array in TypeScript
let arr: number[] = [1, 2, 3, 4, 5];
for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}
// 1
// 2
// 3
// 4
// 5

How to find the maximum and minimum elements in an Array?

The maximum and minimum elements in an array can be found by iterating through the array and comparing each element with the current maximum and minimum elements.

JavaScipt

Written by @Ajay-Dhangar

// Find the maximum and minimum elements in an array in JavaScript
function findMaxMin(arr) {
    let max = arr[0];
    let min = arr[0];
    for (let i = 1; i < arr.length; i++) {
        if (arr[i] > max) {
            max = arr[i];
        }
        if (arr[i] < min) {
            min = arr[i];
        }
    }
    return { max, min };
}

let arr = [2, 5, 1, 20, 10];
console.log(findMaxMin(arr)); // { max: 20, min: 1 }

Java

Written by @Ajay-Dhangar

public class Main {
// Find the maximum and minimum elements in an array in Java
static class MaxMin {
    int max;
    int min;
}

static MaxMin findMaxMin(int arr[]) {
    MaxMin result = new MaxMin();
    result.max = arr[0];
    result.min = arr[0];
    for (int i = 1; i < arr.length; i++) {
        if (arr[i] > result.max) {
            result.max = arr[i];
        }
        if (arr[i] < result.min) {
            result.min = arr[i];
        }
    }
    return result;
}

  public static void main(String[] args) {
      int arr[] = {2, 5, 1, 20, 10};
      MaxMin result = findMaxMin(arr);
      System.out.println("{ max: " + result.max + ", min: " + result.min + " }"); // { max: 20, min: 1 }
  }
}

Python

Written by @Ajay-Dhangar

# Find the maximum and minimum elements in an array in Python
def find_max_min(arr):
    max = arr[0]
    min = arr[0]
    for i in range(1, len(arr)):
        if arr[i] > max:
            max = arr[i]
        if arr[i] < min:
            min = arr[i]
    return {"max": max, "min": min}

  arr = [2, 5, 1, 20, 10]
  print(find_max_min(arr)) # { max: 20, min: 1 }

C

Written by @Ajay-Dhangar

// Find the maximum and minimum elements in an array in C
struct MaxMin {
    int max;
    int min;
};

struct MaxMin findMaxMin(int arr[], int n) {
    struct MaxMin result;
    result.max = arr[0];
    result.min = arr[0];
    for (int i = 1; i < n; i++) {
        if (arr[i] > result.max) {
            result.max = arr[i];
        }
        if (arr[i] < result.min) {
            result.min = arr[i];
        }
    }
    return result;
}

int arr[] = {2, 5, 1, 20, 10};
struct MaxMin result = findMaxMin(arr, 5);
printf("{ max: %d, min: %d }\n", result.max, result.min); // { max: 20, min: 1 }

C++

Written by @Ajay-Dhangar

// Find the maximum and minimum elements in an array in C++
struct MaxMin {
    int max;
    int min;
};

MaxMin findMaxMin(int arr[], int n) {
    MaxMin result;
    result.max = arr[0];
    result.min = arr[0];
    for (int i = 1; i < n; i++) {
        if (arr[i] > result.max) {
            result.max = arr[i];
        }
        if (arr[i] < result.min) {
            result.min = arr[i];
        }
    }
    return result;
}

int arr[] = {2, 5, 1, 20, 10};
MaxMin result = findMaxMin(arr, 5);
cout << "{ max: " << result.max << ", min: " << result.min << " }" << endl; // { max: 20, min: 1 }

TypeScript

Written by @Ajay-Dhangar

// Find the maximum and minimum elements in an array in TypeScript
interface MaxMin {
    max: number;
    min: number;
}

function findMaxMin(arr: number[]): MaxMin {
    let max = arr[0];
    let min = arr[0];
    for (let i = 1; i < arr.length; i++) {
        if (arr[i] > max) {
            max = arr[i];
        }
        if (arr[i] < min) {
            min = arr[i];
        }
    }
    return { max, min };
}

let arr: number[] = [2, 5, 1, 20, 10];
console.log(findMaxMin(arr)); // { max: 20, min: 1 }

📝 Info

• The time complexity of finding the maximum and minimum elements in an array is O(n).
• The space complexity of finding the maximum and minimum elements in an array is O(1).

Problems for Practice

Start Practicing: https://leetcode.com/study-plan/programming-skills

Problem Name	Difficulty	Solution Link
1. Two Sum	Easy	View Solutions
2. Best Time to Buy and Sell Stock	Easy	View Solutions
3. Contains Duplicate	Easy	View Solutions
4. Product of Array Except Self	Medium	View Solutions
5. Maximum Subarray	Easy	View Solutions

Conclusion

In this tutorial, we learned about arrays in data structures and algorithms. We learned how to declare an array, access an array, update an array, find the length of an array, iterate through an array, and find the maximum and minimum elements in an array. Arrays are an important data structure that is used in many algorithms and data structures.