Search a 2D 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.

For example,

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]

Given target = 3, return true.

Code in JAVA:

public class Solution {
    public static boolean searchMatrix(int[][] matrix, int target) {
       if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {
           return false;
       }
       int m = matrix.length; 
       int n = matrix[0].length;
       int start = 0;
       int end = m * n - 1;

       while (start <= end) {
           int mid = (start + end) / 2;
           int midX = mid / n;
           int midY = mid % n;

           if (matrix[midX][midY] == target) {
               return true;
           }
           if (matrix[midX][midY] < target) {
               start = mid + 1;
           } else {
               end = mid - 1;
           }

       }
       return false;

    }
}