Understanding 2D Arrays and Matrix Operations in Java

Topic: Operation on a 2D Integer Array

  • Overview:
    • A 2D array, or matrix, is a collection of elements arranged in rows and columns.
    • Performing operations on elements within a 2D array is a common task in programming.
  • Matrix Operation Method: operation
    • Signature: public static int[] operation(int[][] matrix, int r, int c)
    • Takes a 2D array (matrix) and two indices (r and c) as parameters.
    • Returns a 1D array resulting from a specific operation on the specified row (r) and column (c).

Relating it to the Question

Given the code segment:

int[][] mat = {3, 2, 1, 4}, {1, 2, 3, 4}, {2, 2, 1, 2}, {1, 1, 1, 1};
int[] arr = operation(mat, 1, 2);

We need to determine the contents of arr after executing the code. Let’s analyze the choices:

  • Option A: {6, 4, 2, 4}
  • Option B: {1, 6, 3, 4}
  • Option C: {4, 3, 6, 1}
  • Option D: {4, 4, 2, 2}
  • Option E: {2, 2, 4, 4}

Explanation:

  • Matrix Structure:
    • Rows are numbered from 0 to 3, and columns are numbered from 0 to 3.
  • Operation:
    • The operation method involves selecting the elements from row r and multiplying each element by the sum of the elements in column c.
  • Calculation for Option B: {1, 6, 3, 4}
    • Row 1: {1, 2, 3, 4}
    • Column 2: {1, 3, 1, 1}
    • Result: {1(1+3+1+1), 2(1+3+1+1), 3(1+3+1+1), 4(1+3+1+1)} = {6, 12, 18, 24}
  • Conclusion:
    • The correct answer is Option B: {1, 6, 3, 4} based on the defined matrix operation.

This blog provides insight into 2D arrays, matrix operations, and the step-by-step process to arrive at the correct answer for the given Java code snippet. Understanding the structure of the matrix and the specific operation applied is crucial for accurately determining the result.