Search a 2D Matrix II

给一个排序的2d的数组, 搜索元素, 二分查找的2d版.

public class Solution {
    public boolean searchMatrix(int[][] matrix, int target) {
        if(matrix == null || matrix.length == 0)
            return false;
        int i = 0;
        int j = matrix[0].length-1;
        while(i < matrix.length && j >=0) {
            if(matrix[i][j] > target) 
                j--;
            else if(matrix[i][j] < target)
                i++;
            else
                return true;
        }
        return false;
    }
}