LeetCode: Search in Sorted Matrix

/**
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

Integers in each row are sorted from left to right.
The first integer of each row is greater than the last integer of the previous row.
Example 1:

Input:
matrix = [
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]
target = 3
Output: true
Example 2:

Input:
matrix = [
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]
target = 13
Output: false
*/

public class SearchMatrix{
public boolean searchMatrix(int[][] matrix, int target) {
        if(matrix==null || matrix.length<1){
            return false;
        }
if (matrix[0] == null || matrix[0].length == 0){
            return false;
        }
        //start with first row and last column
        int row = 0, col = matrix[0].length-1;
        while(row<matrix.length && col>=0){
            int val = matrix[row][col];
            if(val==target){
                return true;
            }else if(val<target){
                row++;
            }else{
                col--;
            }
        }
        return false;
    }
}