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

m1
class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if(matrix == null || matrix.length == 0) return false;
        if(matrix[0] == null || matrix[0].length == 0) return false;

        int startRow = 0;
        int endRow = matrix.length - 1;
        int rightRow = 0;
        while(startRow + 1 < endRow) {
            int middleRow = startRow + (endRow - startRow) / 2;
            if(matrix[middleRow][0] == target) return true;
            else if(matrix[middleRow][0] > target) endRow = middleRow;
            else if(matrix[middleRow][0] < target) startRow = middleRow;
        }
        if(matrix[endRow][0] <= target) rightRow = endRow;
        else if(matrix[startRow][0] <= target) rightRow = startRow;
        else return false;

        int startCol = 0;
        int endCol = matrix[rightRow].length - 1;
        while(startCol + 1 < endCol) {
            int middleCol = startCol + (endCol - startCol) / 2;
            if(matrix[rightRow][middleCol] == target)  return true;
            else if(matrix[rightRow][middleCol] > target) endCol = middleCol;
            else if(matrix[rightRow][middleCol] < target) startCol = middleCol;
        }

        if(matrix[rightRow][startCol] == target || matrix[rightRow][endCol] == target) return true;
        return false;
    }
}

m2
class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if(matrix == null || matrix.length == 0) return false;
        if(matrix[0] == null || matrix[0].length == 0) return false;
        int row = matrix.length;
        int col = matrix[0].length;

        int start = 0;
        int end = row * col - 1;

        while(start < end - 1) {
            int mid = start + (end - start) / 2;
            int midRow = mid / col;
            int midCol = mid % col;
            if(matrix[midRow][midCol] == target) return true;
            else if(matrix[midRow][midCol] > target) end = mid;
            else start = mid;
        }

        if(matrix[start / col][start % col] == target || matrix[end / col][end % col] == target) return true;
        return false;
    }
}