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Java Exercises: Searches a value in an m x n matrix

Java Basic: Exercise-120 with Solution

Write a Java program that searches a value in an m x n matrix.

Sample Solution:

Java Code:

public class Main {
public static void main(String[] args) {
 // int target = 5;
  int target = 0;
  int[][] matrix = new int[3][3];
        for (int row = 0; row < 3; row ++)
            for (int col = 0; col < 3; col++)
                matrix[row][col] = (1 + row * 3 + col);

        for (int row = 0; row < 3; row ++)
        {
            for (int col = 0; col < 3; col++)
              {
                System.out.print(matrix[row][col]+" ");
                if (col == 2)
                System.out.println();
              }
        }
      System.out.print(Boolean.toString(searchMatrix(matrix, target))); 
    }
  public static boolean searchMatrix(int[][] matrix, int target) {
        if (matrix.length == 0 || matrix[0].length == 0) {
            return false;
        }
        int m = matrix.length;
        int n = matrix[0].length;
        int lower = 0;
        int higher = m * n - 1;
        while (lower <= higher) {
            int mid = (lower + higher) >> 1;
            int val = matrix[mid / n][mid % n];
            if (val == target) {
                return true;
            }
            if (val < target) {
                lower = mid + 1;
            } else {
                higher = mid - 1;
            }
        }
        return false;
    }
}


Sample Output:

1 2 3 
4 5 6 
7 8 9 
false

Pictorial Presentation:

Java exercises: Searches a value in an m x n matrix
Java exercises: Searches a value in an m x n matrix

Flowchart:

Flowchart: Java exercises: Searches a value in an m x n matrix

Java Code Editor:

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Java: Tips of the Day

getEnumMap

Converts to enum to Map where key is the name and value is Enum itself.

public static <E extends Enum<E>> Map<String, E> getEnumMap(final Class<E> enumClass) {
    return Arrays.stream(enumClass.getEnumConstants())
            .collect(Collectors.toMap(Enum::name, Function.identity()));
}

Ref: https://bit.ly/3xXcFZt