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Create Array_2D
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public class Arrays_2D {
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public static void main(String args[]){
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// please sure to uncomment the examples one by one
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//-----------------------------TODO: Example_1----------------------------------
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// TODO: Manually allocate differing size second dimensions (columns).
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int[][] twoD = new int[4][];
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twoD[0] = new int[1]; // one column for first row
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twoD[1] = new int[2]; // two columns for second row
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twoD[2] = new int[3]; // three columns for third row
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twoD[3] = new int[4]; // four columns for fourth row
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int i, j, k = 0;
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// add items (values) to the array
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for(i=0; i<4; i++) {
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for (j = 0; j < i + 1; j++) {
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twoD[i][j] = k;
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k++;
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}
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}
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// print the array
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for(i=0; i<4; i++) {
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for(j=0; j<i+1; j++)
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System.out.print(twoD[i][j] + " ");
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System.out.println();
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}
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// ---------------------------TODO: Example_2--------------------------
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Accessing elements using nested loops
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// System.out.print(matrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -------------------------TODO: Example_3--------------------------------
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// TODO: Initializing a 2D Array with User Input
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// Scanner scanner = new Scanner(System.in);
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// // Get the dimensions of the 2D array from the user
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// System.out.print("Enter the number of rows: ");
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// int rows = scanner.nextInt();
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// System.out.print("Enter the number of columns: ");
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// int columns = scanner.nextInt();
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// // Initialize a 2D array based on user input
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// int[][] userArray = new int[rows][columns];
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// // Populate the array with user input
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// System.out.println("Enter the elements of the array:");
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// for (int i = 0; i < rows; i++) {
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// for (int j = 0; j < columns; j++) {
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// userArray[i][j] = scanner.nextInt();
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// }
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// }
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// // Display the user-initialized 2D array
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// System.out.println("User-Initialized 2D Array:");
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// for (int i = 0; i < rows; i++) {
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// for (int j = 0; j < columns; j++) {
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// System.out.print(userArray[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -----------------------------TODO: Example_4----------------------------
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// TODO: Sum of Elements in a 2D Array
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// Calculating the sum of all elements
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// int sum = 0;
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// int sum_all = 0;
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// sum_all += matrix[i][j];
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// sum += matrix[i][j]; // sum of every row
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// }
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// System.out.println("sum of row ["+i+"]"+sum);
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// sum=0;
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// }
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// System.out.println("Sum of all elements: " + sum_all);
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// ---------------------------TODO: Example_5------------------------------
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// TODO: Finding the Maximum Element
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// int[][] matrix = {
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// {3, 7, 1},
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// {8, 2, 5},
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// {4, 6, 9}
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// };
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// // Finding the maximum element
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// int max = matrix[0][0];
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// if (matrix[i][j] > max) {
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// max = matrix[i][j];
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// }
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// }
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// }
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// System.out.println("Maximum element: " + max);
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// ---------------------------TODO: Example_6------------------------------
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// TODO: Transposing a Matrix (swapping its rows with its columns)
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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//// Transposing the matrix
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// int[][] transposedMatrix = new int[matrix[0].length][matrix.length];
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// transposedMatrix[j][i] = matrix[i][j];
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// }
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// }
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// for (int i = 0; i < transposedMatrix.length; i++) {
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// for (int j = 0; j < transposedMatrix[i].length; j++) {
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// System.out.print(transposedMatrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// ----------------------------TODO: Example_7-----------------------------
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// TODO: Matrix Addition (the operation of adding two matrices by adding their corresponding elements)
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// int[][] matrix1 = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// int[][] matrix2 = {
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// {9, 8, 7},
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// {6, 5, 4},
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// {3, 2, 1}
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// };
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// // Performing matrix addition
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// int[][] resultMatrix = new int[matrix1.length][matrix1[0].length];
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// for (int i = 0; i < matrix1.length; i++) {
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// for (int j = 0; j < matrix1[i].length; j++) {
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// resultMatrix[i][j] = matrix1[i][j] + matrix2[i][j];
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// }
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// }
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// // Displaying the result matrix
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// System.out.println("Matrix Addition Result:");
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// for (int i = 0; i < resultMatrix.length; i++) {
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// for (int j = 0; j < resultMatrix[i].length; j++) {
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// System.out.print(resultMatrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -----------------------------TODO: Example_8----------------------------
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// TODO: Matrix Multiplication
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// int[][] matrix1 = {
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// {1, 2},
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// {3, 4},
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// {5, 6}
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// };
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// int[][] matrix2 = {
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// {7, 8, 9},
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// {10, 11, 12}
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// };
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// // Performing matrix multiplication
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// int[][] resultMatrix = new int[matrix1.length][matrix2[0].length];
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// for (int i = 0; i < matrix1.length; i++) {
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// for (int j = 0; j < matrix2[0].length; j++) {
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// for (int k = 0; k < matrix1[0].length; k++) {
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// resultMatrix[i][j] += matrix1[i][k] * matrix2[k][j];
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// }
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// }
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// }
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// // Displaying the result matrix
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// System.out.println("Matrix Multiplication Result:");
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// for (int i = 0; i < resultMatrix.length; i++) {
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// for (int j = 0; j < resultMatrix[i].length; j++) {
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// System.out.print(resultMatrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -----------------------------TODO: Example_9----------------------------
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// TODO: Matrix Scalar Multiplication
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// Initializing a matrix
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Performing scalar multiplication
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// int scalar = 2;
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// int[][] resultMatrix = new int[matrix.length][matrix[0].length];
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// resultMatrix[i][j] = scalar * matrix[i][j];
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// }
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// }
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// // Displaying the result matrix
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// System.out.println("Scalar Multiplication Result:");
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// for (int i = 0; i < resultMatrix.length; i++) {
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// for (int j = 0; j < resultMatrix[i].length; j++) {
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// System.out.print(resultMatrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -----------------------------TODO: Example_10----------------------------
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// TODO: Finding the Sum of Each Row in a 2D Array
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Finding the sum of each row
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// for (int i = 0; i < matrix.length; i++) {
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// int rowSum = 0;
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// for (int j = 0; j < matrix[i].length; j++) {
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// rowSum += matrix[i][j];
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// }
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// System.out.println("Sum of elements in Row " + (i + 1) + ": " + rowSum);
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// }
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// ---------------------------TODO: Example_11------------------------------
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// TODO: Rotating a Matrix 90 Degrees
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// Initializing a 3x3 matrix
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Rotating the matrix 90 degrees clockwise
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// int[][] rotatedMatrix = new int[matrix[0].length][matrix.length];
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// rotatedMatrix[j][matrix.length - 1 - i] = matrix[i][j];
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// }
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// }
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// // Printing the rotated matrix
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// for (int i = 0; i < rotatedMatrix.length; i++) {
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// for (int j = 0; j < rotatedMatrix[i].length; j++) {
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// System.out.print(rotatedMatrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// -----------------------------TODO: Example_12----------------------------
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// TODO: finding the sum of each column
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Finding the sum of each column
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// int columns = matrix[0].length;
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// for (int j = 0; j < columns; j++) {
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// int columnSum = 0;
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// for (int i = 0; i < matrix.length; i++) {
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// columnSum += matrix[i][j];
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// }
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// System.out.println("Sum of elements in Column " + (j + 1) + ": " + columnSum);
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// }
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// ---------------------------TODO: Example_13------------------------------
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// TODO: Transposing a 2D Array Without Creating a New Array
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// int[][] matrix = {
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// {1, 2, 3},
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// {4, 5, 6},
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// {7, 8, 9}
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// };
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// // Transposing the matrix in-place
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = i + 1; j < matrix[i].length; j++) {
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// // Swap elements at (i, j) and (j, i)
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// int temp = matrix[i][j];
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// matrix[i][j] = matrix[j][i];
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// matrix[j][i] = temp;
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// }
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// }
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// // Displaying the transposed matrix
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// System.out.println("In-Place Transposed Matrix:");
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// for (int i = 0; i < matrix.length; i++) {
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// for (int j = 0; j < matrix[i].length; j++) {
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// System.out.print(matrix[i][j] + " ");
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// }
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// System.out.println();
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// }
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// ---------------------------TODO: Example_14------------------------------
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// TODO: Finding the Sum of Diagonals in a Square Matrix
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// Initializing a 4x4 matrix
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// int[][] matrix = {
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// {1, 2, 3, 4},
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// {5, 6, 7, 8},
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// {9, 10, 11, 12},
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// {13, 14, 15, 16}
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// };
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// int primaryDiagonalSum = 0;
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// int secondaryDiagonalSum = 0;
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// // Calculating the sum of the primary diagonal
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// for (int i = 0; i < matrix.length; i++) {
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// primaryDiagonalSum += matrix[i][i];
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// }
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// // Calculating the sum of the secondary diagonal
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// for (int i = 0; i < matrix.length; i++) {
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// secondaryDiagonalSum += matrix[i][matrix.length - 1 - i];
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// }
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// System.out.println("Sum of primary diagonal: " + primaryDiagonalSum);
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// System.out.println("Sum of secondary diagonal: " + secondaryDiagonalSum);
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}
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}

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