Java implementation LeetCode 74 search a two-dimensional matrix

74. The two-dimensional matrix search

Prepared by an efficient algorithm to determine the mxn matrix, the presence or absence of a target value. This matrix has the following characteristics:

An integer of from left to right in each row in ascending order.
The first integer is greater than the last row of each integer previous row.
Example 1:

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

Input:
Matrix = [
[. 1,. 3,. 5,. 7],
[10,. 11, 16, 20 is],
[23 is, 30, 34 is, 50]
]
target = 13 is
output: false

class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if (matrix.length == 0 || matrix[0].length == 0)
            return false;
        int begin, mid, end;
        begin = mid = 0;
        int len1 = matrix.length, len2 = matrix[0].length;
        end = len1 * len2 - 1;
        while (begin < end) {
            mid = (begin + end) / 2;
            if (matrix[mid / len2][mid % len2] < target)
                begin = mid + 1;
            else
                end = mid;
        }
        return matrix[begin / len2][begin % len2] == target;
    }
}