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Java,C++,Python & C
Array Data Structure

Array in C/C++/java/Python

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All About Array

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1D_arrays

2D_arrays

arraylist

Declare an Array

    1. Declaring array then allocation memory for it and then initializing it.
 
int intArray[];
intArray = new int[20];
    1. Declaration and allocation memory for array in one line then initializing it.
 
int intArray[] = new int[5];
arr1[0] = 10;
arr1[1] = 20;
arr1[2] = 30;
arr1[3] = 40;
arr1[4] = 50;
    1. Declaration , instantiation and initialization in one line.
 
int intArray[] = new int[]{10, 20, 30, 40, 50};
    1. Declaration , instantiation and initialization in one line.
 
int intArray[] = {10, 20, 30, 40, 50};
    1. 2D Array Declaration and initialization in one line.
int intArray[][] = {{1,2,3},{4,5,6},{7,8,9}};
    1. 2D Array first declaration then allocation memory for it and then initialization.
int intArray[][];
intArray = new int[3][3];
intArray[0][0] = 1;
intArray[0][1] = 2;
intArray[0][2] = 3;
intArray[1][0] = 4;
intArray[1][1] = 5;
intArray[1][2] = 6;
intArray[2][0] = 7;
intArray[2][1] = 8;
intArray[2][2] = 9;
    1. 2D Array first declaration then allocation memory for it and then initialization.

Access Elements of Arrays

    1. You can access elements with the help of the index at which you stored them
 
int[] arr = {1, 2, 3, 4, 5};
System.out.println(arr[0] + " " + arr[1] + " "+ arr[2] + " " + arr[3] + " " + arr[4]);
    1. You can access elements with the help of normal for loop
 
   int[] arr = {1, 2, 3, 4, 5};
 
  for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
    1. You can access elements with the help of for-each loop
 
   int[] arr = {1, 2, 3, 4, 5};
 
  for (int i : arr) {
            System.out.print(i + " ");
   }
    1. You can access elements with the help of while loop
 
   int[] arr = {1, 2, 3, 4, 5};
 
   int i = 0;
        while (i < arr.length) {
            System.out.print(arr[i] + " ");
            i++;
        }
    1. You can access elements with the help of do-while loop
   int[] arr = {1, 2, 3, 4, 5};
 
   int j = 0;
        do {
            System.out.print(arr[j] + " ");
            j++;
        } while (j < arr.length);
    1. You can access elements with the help of Passing Arrays to Methods
class CodeXam {
    public static void printArray (int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i]);
        }
    }
    public static void main(String args[]) {
        int[] arr = {1, 2, 3, 4, 5};
        printArray(arr);
    }
}
    1. 2D Array Accessing Elements
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
System.out.println(arr[0][0] + " " + arr[0][1] + " "+ arr[0][2] + " " + arr[1][0] + " " + arr[1][1] + " " + arr[1][2] + " " + arr[2][0] + " " + arr[2][1] + " " + arr[2][2]);
    1. 2D Array Accessing Elements with the help of for loop
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) {
                System.out.print(arr[i][j] + " ");
            }
        }
    1. 2D Array Accessing Elements with the help of for-each loop
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
for (int[] i : arr) {
            for (int j : i) {
                System.out.print(j + " ");
            }
        }
    1. 2D Array Accessing Elements with the help of while loop
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
int i = 0;
        while (i < arr.length) {
            int j = 0;
            while (j < arr[i].length) {
                System.out.print(arr[i][j] + " ");
                j++;
            }
            i++;
        }
    1. 2D Array Accessing Elements with the help of do-while loop
int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
int i = 0;
        do {
            int j = 0;
            do {
                System.out.print(arr[i][j] + " ");
                j++;
            } while (j < arr[i].length);
            i++;
        } while (i < arr.length);
    1. 2D Array Accessing Elements with the help of Passing Arrays to Methods
class CodeXam {
    public static void printArray (int[][] arr) {
        for (int i = 0; i < arr.length; i++) {
            for (int j = 0; j < arr[i].length; j++) {
                System.out.print(arr[i][j] + " ");
            }
        }
    }
    public static void main(String args[]) {
        int[][] arr = {{1,2,3},{4,5,6},{7,8,9}};
        printArray(arr);
    }
}

Traversal

CodeXam.cpp
 
#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cout << "Enter no. of elements you want in array:";
    cin >> n;
    int a[n];
    cout << "Enter all the elements:" << endl;
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];
    }
    cout << "Elements in array are:" << endl;
    for (int i = 0; i < n; i++)
    {
        cout << a[i] << endl;
    }
    return 0;
}

output

Enter the number of elements in array: 5
Enter the element: 2
Enter the element: 2
Enter the element: 3
Enter the element: 3
Enter the element: 2
Elements in array are:
2
2
3
3
2

Insertion

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int arr[] = {45,25,26,75};
    int n = sizeof(arr)/sizeof(arr[0]);
    cout << "Before Array" << endl;
    for (int i = 0 ; i < n ; i++){
        cout << arr[i] << " ";
    }
    cout << endl;
    int pos = 2;
    int element = 69;
    int newArr[n+1];
    for (int i = 0 ; i < pos ; i++){
        newArr[i] = arr[i];
    }
    newArr[pos] = element;
    for (int i = pos; i <n ; i++){
        newArr[i+1] = arr[i];
    }
    cout << "After Array" << endl;
    for (int i = 0 ; i < n+1 ; i++){
        cout << newArr[i] << " ";
    }
    cout << endl;
    return 0;
}

output

Before Array[45, 25, 26, 75]
After Array[45, 25, 69, 26, 75]

Deletion

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int arr[] = {12, 212, 30, 44, 56};
    int pos = 3;
    int n = sizeof(arr)/sizeof(arr[0]);
    cout << "Before deletion" << endl;
    for(int i = 0; i < n; i++){
        cout << arr[i] << " ";
    }
    cout << endl;
    int newArr[n-1];
    for(int i = 0; i < pos-1; i++){
        newArr[i] = arr[i];
    }
    for(int i = pos; i < n; i++){
        newArr[i-1] = arr[i];
    }
    cout << "After deletion" << endl;
    for(int i = 0; i < n-1; i++){
        cout << newArr[i] << " ";
    }
    cout << endl;
    return 0;
}

output

Before deletion[12, 212, 30, 44, 56]
After deletion[12, 212, 44, 56]

Searching

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int arr[] = {1,2,3,4,5};
    int n = sizeof(arr)/sizeof(arr[0]);
    cout<<"The array is: ";
    for(int i = 0; i < n; i++){
        cout<<arr[i]<<" ";
    }
    cout<<endl;
    cout<<"Enter the element to be searched: ";
    int element;
    cin>>element;
    int index = -1;
    for(int i = 0; i < n; i++){
        if(arr[i] == element){
            index = i;
            break;
        }
    }
    if(index == -1){
        cout<<"Element not found";
    }
    else{
        cout<<"Element found at index "<<index;
    }
    return 0;
}

output

The array is:  [1, 2, 3, 4, 5]
Enter the element to be searched: 4
Element found at index  3

Update

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int arr[] = {1,2,3,4,5};
    int index = 2;
    int newValue = 6;
    cout<<"Before update: ";
    for(int i=0; i<5; i++){
        cout<<arr[i]<<" ";
    }
    cout<<endl;
    for(int i=0; i<5; i++){
        if(i == index){
            arr[i] = newValue;
            break;
        }
    }
    cout<<"After update: ";
    for(int i=0; i<5; i++){
        cout<<arr[i]<<" ";
    }
    cout<<endl;
    return 0;
}

output

Before update: [1, 2, 3, 4, 5]
After update: [1, 2, 6, 4, 5]

Sort

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int arr[] = { 21 , 52 , 83 , 48 , 15};
    int n = sizeof(arr)/sizeof(arr[0]);
    sort(arr, arr+n);
    cout << "Ascending order sorting of array" << endl;
    for (int i = 0; i < n; i++) {
        cout << arr[i] << " ";
    }
    cout << endl;
    cout << "Descending order sorting of array" << endl;
    for (int i = n-1; i >= 0; i--) {
        cout << arr[i] << " ";
    }
    return 0;
}

output

Ascending order sorting of array
15 21 48 52 83
Descending order sorting of array
83 52 48 21 15

Array - 2D

CodeXam.cpp
#include <bits/stdc++.h>
using namespace std;
 
int main(){
    int row, column;
    cout << "Enter the number of rows" << endl;
    cin >> row;
    cout << "Enter the number of column" << endl;
    cin >> column;
    cout << "Enter the elements" << endl;
    int arr[row][column];
    for (int i = 0 ; i < row  ; i++){
        for (int j = 0 ; j < column ; j++){
            cin >> arr[i][j];
        }
    }
 
    for (int i = 0 ; i < row  ; i++){
        for (int j = 0 ; j < column ; j++){
            cout << arr[i][j] << " ";
        }
        cout << endl;
    }
}

output

Enter the number of rows
2
Enter the number of column
3
Enter the elements
12
56
25
25
36
38
12 56 25
25 36 38

Basic Questions

Reverse an Array

Approach

Reverse an Array Using Swapping

Code

CodeXam.cpp
#include<iostream>
using namespace std;
 
int main() {
    int n;
    cout << "Enter the number of the elements you want to add in the array: ";
    cin >> n;
    int arr[n];
    cout << "Enter the elements of the array: ";
    for (int i = 0; i < n; i++) {
        cin >> arr[i];
    }
    int l = sizeof(arr) / sizeof(arr[0]);
    int k = l / 2;
    int temp;
    for (int i = 0; i < k; i++) {
        temp = arr[i];
        arr[i] = arr[l - i - 1];
        arr[l - i - 1] = temp;
    }
    cout << "Reversed array is: ";
    for (int i = 0; i < n; i++) {
        cout << arr[i] << " ";
    }
    return 0;
}

output

Enter the number of the elements you want to add in the array:
5
Enter the elements of the array:
12
13
14
15
16
Reversed array is:
16 15 14 13 12

Maximum and Minimum

Approach

    1. Initialize max and min with the first element of the array.
    1. Traverse the array from the first index to the last index. 0->arr.length
    1. If the current element is greater than max, then update max.
    1. If the current element is smaller than min, then update min.
    1. Print the maximum and minimum element of the array.

Code

CodeXam.cpp
#include <iostream>
using namespace std;
 
int main()
{
    int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    int max = arr[0];
    int min = arr[0];
    for (int i = 0; i < 10; i++) {
        if (arr[i] > max) {
            max = arr[i];
        }
        if (arr[i] < min) {
            min = arr[i];
        }
    }
    cout << "Max element in the array is " << max << endl;
    cout << "Min element in the array is " << min << endl;
    return 0;
}

output

Max element in the array is 10
Min element in the array is 1

Check Sorted or Not

Approach

    1. Traverse the array from the first index to the last index. 0->arr.length
    1. If the current element is greater than the next element, then the array is not sorted.
    1. If the current element is smaller than the next element, then the array is sorted.
    1. Print the result.

Code

CodeXam.cpp
#include <iostream>
using namespace std;
 
int main()
{
    int arr[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    for (int i = 0; i < sizeof(arr) / sizeof(arr[0]) - 1; i++)
    {
        if (arr[i] > arr[i + 1])
        {
            cout << "Not Sorted";
            return 0;
        }
    }
    cout << "Sorted";
    return 0;
}

output

Sorted

Search Number in The Matrix

Approach

Take a matrix as input from the user and search for a given number in the matrix and print the position of the number if found.

    1. Take the number of rows and columns as input from the user.
    1. Take the elements of the matrix as input from the user.
    1. Take the number to be searched as input from the user.
    1. Traverse the matrix and check if the number is present in the matrix.
    1. If the number is present in the matrix, then print the position of the number.
    1. If the number is not present in the matrix, then print that the number is not present in the matrix.

Code

CodeXam.cpp
#include <iostream>
using namespace std;
 
int main()
{
    int row, column, number, flag = 0;
    cout << "Enter the number of rows and columns of the matrix" << endl;
    cin >> row >> column;
    int matrix[row][column];
    cout << "Enter the elements of the matrix" << endl;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < column; j++)
        {
            cin >> matrix[i][j];
        }
    }
    cout << "Enter the number to be searched" << endl;
    cin >> number;
    for (int i = 0; i < row; i++)
    {
        for (int j = 0; j < column; j++)
        {
            if (matrix[i][j] == number)
            {
                cout << "The number is found at position " << i + 1 << "," << j + 1 << endl;
                flag = 1;
            }
        }
    }
 
    if (flag == 0)
    {
        cout << "The number is not found" << endl;
    }
 
    return 0;
}

output

Enter the number of rows and columns of the matrix
2
2
Enter the elements of the matrix
12
13
14
25
Enter the number to be searched
14
The number is found at position 2,1

Any Matrix Addition

Approach

    1. Take the number of rows and columns of the matrix as input from the user.
    1. Take the elements of the first matrix as input from the user.
    1. Take the elements of the second matrix as input from the user.
    1. Add the elements of the first matrix and the second matrix and store the result in a third matrix.
    1. Print the third matrix.

Code

CodeXam.cpp
#include <iostream>
using namespace std;
 
int main()
{
   int row, column, i, j;
    cout << "Enter the number of rows" << endl;
    cin >> row;
    cout << "Enter the number of columns" << endl;
    cin >> column;
 
    int matrix1[row][column];
    int matrix2[row][column];
    int sum[row][column];
 
    cout << "Enter the elements of matrix1" << endl;
 
    for (i = 0; i < row; i++) {
        for (j = 0; j < column; j++) {
            cin >> matrix1[i][j];
        }
    }
 
    cout << "Enter the elements of matrix2" << endl;
 
    for (i = 0; i < row; i++) {
        for (j = 0; j < column; j++) {
            cin >> matrix2[i][j];
        }
    }
 
    for (i = 0; i < row; i++) {
        for (j = 0; j < column; j++) {
            sum[i][j] = matrix1[i][j] + matrix2[i][j];
        }
    }
 
    cout << "Sum of the matrices:" << endl;
 
    for (i = 0; i < row; i++) {
        for (j = 0; j < column; j++) {
            cout << sum[i][j] << " ";
        }
        cout << endl;
    }
 
    return 0;
 
}

output

Enter the number of rows: 2
Enter the number of columns: 2
Enter the elements of matrix1
12
13
14
15
Enter the elements of matrix2
1
2
3
4
Sum of the matrices:
13 15
17 19
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