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`

.

public class Solution { public 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 start = 0; int end = m * n - 1; while (start <= end) { int mid = (start + end) / 2; int midVal = matrix[mid / n][mid % n]; if (midVal == target) { return true; } else if (midVal > target) { end = mid - 1; } else { start = mid + 1; } } return false; } }

Note: O(log(m*n))