Question

You will implement the following method

public static int[] linearSearchExtended(int[][] numbers, int key) {
// Implement this method
return new int[] {};

}   
There is a utility method provided for you with the following signature. You may use this method to convert a list of integers into an array.

public static int[] convertIntegers(List<Integer> integers)

Provided code

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class MatrixSearch {

// This method converts a list of integers to an array of integers
// Do not change this method
   public static int[] convertIntegers(List<Integer> integers) {
       int[] ret = new int[integers.size()];
       Iterator<Integer> iterator = integers.iterator();
       for(int i = 0; i < ret.length; i++) {
           ret[i] = iterator.next().intValue();
       }
       return ret;
   }  

// Search for a key in a matrix and returns all the indices in an array
// The indices are converted into a linear form.
   public static int[] linearSearchExtended(int[][] numbers, int key) {
   // Implement this method
   return new int[] {};
  
   }  

  
   public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
      
       int nRow, nColumn = 0;
       do {
           System.out.println("Both the row and column must be > 0");
           nRow = input.nextInt();
           nColumn = input.nextInt();
       } while (nRow <= 0 || nColumn <= 0);
       int[][] numbers = new int[nRow][nColumn];
       for (int i = 0; i < nRow; i++) {
           for(int j = 0; j < nColumn; j++) {
               numbers[i][j] = input.nextInt();
           }
       }

/*       System.out.println("The matrix contains: ");
       for (int i = 0; i < nRow; ++i) {
           for(int j = 0; j < nColumn; j++) {
               System.out.printf("%5d", numbers[i][j]);
           }
           System.out.println();
       }
       System.out.println();
*/
       System.out.printf("Enter a search key:%n ");
       int key = input.nextInt();

       int[] allIndices = linearSearchExtended(numbers, key);

       if(allIndices.length == 0) {
           System.out.printf("%d not found!%n", key);
       } else {
           System.out.printf("Found %d at index: ", key);
           for(int i = 0; i < allIndices.length; i++) {
               System.out.printf("%d ", allIndices[i]);
           }
       }
   }
}

Sample Input
4
5

63 -95 9 -80 77
-27 85 -57 -83 73
99 -57 -4 19 -75
35 -45 37 24 71

19

Sample Output
Found 19 at index: 13

Explanation

Considering the rows of the matrix as contiguous arrays (row 0 has index 0 to 4, row 1 has index 5 to 9, and so on), the index of 19 is 13.

Answer 1

Given below is the code for the question.
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import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class MatrixSearch {

// This method converts a list of integers to an array of integers
// Do not change this method
public static int[] convertIntegers(List<Integer> integers) {
int[] ret = new int[integers.size()];
Iterator<Integer> iterator = integers.iterator();
for(int i = 0; i < ret.length; i++) {
ret[i] = iterator.next().intValue();
}
return ret;
}

// Search for a key in a matrix and returns all the indices in an array
// The indices are converted into a linear form.
public static int[] linearSearchExtended(int[][] numbers, int key) {
// Implement this method
int rows = numbers.length, cols = numbers[0].length;
ArrayList<Integer> indices = new ArrayList<Integer>();
for(int r = 0; r < rows; r++){
for(int c = 0; c < cols; c++){
if(numbers[r][c] == key){
indices.add(r*cols + c);
}
}
}
return convertIntegers(indices);
}

  
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
  
int nRow, nColumn = 0;
do {
System.out.println("Both the row and column must be > 0");
nRow = input.nextInt();
nColumn = input.nextInt();
} while (nRow <= 0 || nColumn <= 0);
int[][] numbers = new int[nRow][nColumn];
for (int i = 0; i < nRow; i++) {
for(int j = 0; j < nColumn; j++) {
numbers[i][j] = input.nextInt();
}
}

/* System.out.println("The matrix contains: ");
for (int i = 0; i < nRow; ++i) {
for(int j = 0; j < nColumn; j++) {
System.out.printf("%5d", numbers[i][j]);
}
System.out.println();
}
System.out.println();
*/
System.out.printf("Enter a search key:%n ");
int key = input.nextInt();

int[] allIndices = linearSearchExtended(numbers, key);

if(allIndices.length == 0) {
System.out.printf("%d not found!%n", key);
} else {
System.out.printf("Found %d at index: ", key);
for(int i = 0; i < allIndices.length; i++) {
System.out.printf("%d ", allIndices[i]);
}
}
}
}

output
----
Both the row and column must be > 0
4
5
63 -95 9 -80 77
-27 85 -57 -83 73
99 -57 -4 19 -75
35 -45 37 24 71

Enter a search key:
19
Found 19 at index: 13