Start from top right corner of the matrix. Move left if the target is smaller and move down if the target is greater.

```
class Solution(object):
def searchMatrix(self, matrix, target):
"""
:type matrix: List[List[int]]
:type target: int
:rtype: bool
"""
if not matrix:
return False
m = len(matrix)
n = len(matrix[0])
j = n - 1
i = 0
while j >= 0 and i < m:
if matrix[i][j] == target:
return True
if matrix[i][j] > target:
j -= 1
else:
i += 1
return False
```