A matrix is a scalar matrix, if all elements of the diagonal are the same and all elements except the diagonal elements are 0. Given matrix mat, check if the matrix is a scalar matrix.
| Input1 |
Expected outputs |
mat = {
{3,0,0},
{0,3,0},
{0,0,3}}
|
The matrix is a Scalar Matrix.
|
mat= {
{55,0,0,0},
{0,55,0,0},
{0,0,55,0},
{0,0,55,55}}
|
The matrix is *not* a Scalar Matrix.
|
mat={
{30,40},
{50,30}}
|
The matrix is *not* a Scalar Matrix.
|
| The java method should accept following input parameters: mat (integer matrix).
|
| Initialize int variable diag to mat[0][0].
|
| Iterate through mat 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 < mat.length:
o Iterate through mat 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 < mat[0].length:
Check if (rIdx==cIdx):
If mat[rIdx][cIdx] != diag, return false, exit program.
Check if (rIdx != cIdx):
If mat[rIdx][cIdx] != 0, return false, exit program.
|
| If above loops are completed without intermediate return/exit, it means the input matrix is a scalar matrix so, return true.
|
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 MdArrayCheckScalar {
public boolean matArrayCheckScalar(int[][] mat) throws Exception{
int diag=mat[0][0];
for (int rIdx=0; rIdx < mat.length; rIdx++) {
for (int cIdx=0; cIdx < mat[0].length; cIdx++) {
if (rIdx==cIdx) {
if (mat[rIdx][cIdx] != diag) {
return false;
}
}else {
if (mat[rIdx][cIdx] != 0) {
return false;
}
}
}
}
return true;
}
public static void main(String[] args) {
MdArrayCheckScalar ap=new MdArrayCheckScalar();
boolean ret;
try {
int[][] arr = { {3,0,0},
{0,3,0},
{0,0,3}
};
print2dArray(arr, "The 2d Array");
ret=ap.matArrayCheckScalar(arr);
if (ret) {
System.out.println("\n The matrix is an Scalar Matrix");
}else {
System.out.println("\n The matrix is *not* an Scalar Matrix");
}
int[][] arr1 = { {55,0,0,0},
{0,55,0,0},
{0,0,55,0},
{0,0,55,55}};
print2dArray(arr1, "The 2d Array");
ret=ap.matArrayCheckScalar(arr1);
if (ret) {
System.out.println("\n The matrix is an Scalar Matrix");
}else {
System.out.println("\n The matrix is *not* an Scalar Matrix");
}
int[][] arr2 = { {30,40},
{50,30},
};
print2dArray(arr2, "The 2d Array");
ret=ap.matArrayCheckScalar(arr2);
if (ret) {
System.out.println("\n The matrix is an Scalar Matrix");
}else {
System.out.println("\n The matrix is *not* an Scalar Matrix");
}
}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;
}
}