searching in 2d array as O(n) with unsorted rows

Question

I need to write a method that takes 2d array \'int [][] m\' and a value \'val\' and check if val is in the array in the complexity of O(n) while n defined as the num

Answer 1

Smth. like that. In case of Every number at row i is equals or smaller then every number on row i+1, than you can check only first element in each row to define a row, where required value could be. Element in unsorted row can be found only with full scan.

This algorithm have to scan 2 full rows only, which is O(n) where n - number of rows.

public static boolean findValTest(int[][] m, int val) {
    for (int row = 0; row < m.length; row++) {
        if (m[row][0] <= val && row != m.length - 1)
            continue;

        int r = row;

        while (r >= row - 1 && r >= 0) {
            for (int col = 0; col < m[r].length; col++)
                if (m[r][col] == val)
                    return true;

            r--;
        }

        return false;
    }

    return false;
}

Test cases:

System.out.println(findValTest(arr3, -1)); // false
System.out.println(findValTest(arr3, 5)); // true
System.out.println(findValTest(arr3, 7)); // true
System.out.println(findValTest(arr3, 55)); // false
System.out.println(findValTest(arr3, 47)); // true
System.out.println(findValTest(arr3, 147)); // true
System.out.println(findValTest(arr3, 200)); // false
System.out.println(findValTest(new int[][] { { 3, 4, 5 } }, 4));   // true