CC-4 : Add 2 matrices.

Description:

Given 2 matrices: mat1 and mat2, add the individual elements of the matrix and return a matrix with the sum of individual elements.

Test cases and expected outputs:

Input1	Input2	Expected outputs
mat = { {1,1,4,1}, {9,9,3,0}, {2,1,4,3}}	mat = { {1,1,1,1}, {2,2,2,2}, {3,3,3,3}}	2,2,5,2, 11,11,5,2, 5,4,7,6,
mat= { {-1,-1,}, {4,5}, {3,1}}	mat= { {1,7}, {8,2}, {6,4}}	0,6, 12,7, 9,5,

Pseudocode:

The java method should accept following input parameters: mat1 (integer matrix), mat2 (integer matrix).

Initialise a matrix retMat for storing the matrix with sum of respective elements of the input matrices.

Iterate through mat1 using a for loop, using variable rIdx as loop counter. Loop variable rIdx will be initialized with value 0 and will iterate through all the matrix’s columns one by one till rIdx < mat1.length:

Iterate through mat1 using a for loop, using variable cIdx as loop counter. Loop variable cIdx will be initialized with value 0 and will iterate through all the matrix’s columns one by one till cIdx < mat1[0].length:

Set retMat[rIdx][cIdx]=mat1[rIdx][cIdx]+mat2[rIdx][cIdx].

Once above loops are completed, return retMat as it contains sum of individual elements of mat1 and mat2.

Code:

public int[][] matArrayAddition(int[][] mat1, int[][] mat2) throws Exception{
	int[][] retMat=new int[mat1.length][mat1[0].length];
	for (int oIdx=0; oIdx < mat1.length; oIdx++) {
		for (int iIdx=0; iIdx < mat1[0].length; iIdx++) {
			retMat[oIdx][iIdx]=mat1[oIdx][iIdx]+mat2[oIdx][iIdx];
		}
	}
	return retMat;
}

Click here to download and run code and test cases !

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

public class MdArrayAddition {
	
public int[][] matArrayAddition(int[][] mat1, int[][] mat2) throws Exception{
	int[][] retMat=new int[mat1.length][mat1[0].length];
	for (int oIdx=0; oIdx < mat1.length; oIdx++) {
		for (int iIdx=0; iIdx < mat1[0].length; iIdx++) {
			retMat[oIdx][iIdx]=mat1[oIdx][iIdx]+mat2[oIdx][iIdx];
		}
	}
	return retMat;
}
	
public static void main(String[] args) {
	MdArrayAddition ap=new MdArrayAddition();
	int[][] retArr;
	try {
	int[][] arr1 = {{1,1,4,1},
					{9,9,3,0},	
					{2,1,4,3}							
	};
	int[][] arr2 = {	{1,1,1,1},
						{2,2,2,2},	
						{3,3,3,3}							
	};
	print2dArray(arr1, "The 2d Array");
	print2dArray(arr2, "The 2d Array");
	retArr=ap.matArrayAddition(arr1,arr2);
	print2dArray(retArr, "The Added 2d Array");
			
		
	int[][] arr3 = {{-1,-1,},
					{4,5},	
					{3,1}							
	};
	int[][] arr4 = {	{1,7},
						{8,2},	
						{6,4}							
	};
	print2dArray(arr3, "The 2d Array");
	print2dArray(arr4, "The 2d Array");
	retArr=ap.matArrayAddition(arr3,arr4);
	print2dArray(retArr, "The Added 2d Array");
			
	}catch (Exception exception) {
	System.out.print("Exception,"+ exception);
	exception.printStackTrace();
				
	}
}
	

public static void print2dArray(int[][] intArray, String label) throws Exception {
   	// Case 1: The input Array is null !!
	if (intArray == null) { System.out.println("\n\n Input 2d Array was null !! \n"); return; }
	// Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("*********************************************************************");
	System.out.print(label+" : \n");
	int rIdx=0; int cIdx=0;
	for (rIdx=0; rIdx < intArray.length; rIdx++) {
		for (cIdx=0; cIdx < intArray[rIdx].length; cIdx++) {
			System.out.print(intArray[rIdx][cIdx]);
			if (cIdx < intArray[rIdx].length) System.out.print(",");
		}
		System.out.print("\n");
	} 
	System.out.println();
	System.out.println("**********************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;	
}			
			
}