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 in ascending from left to right.
Integers in each column are sorted in ascending from top to bottom.
For example,
Consider the following matrix:
[
[1, 4, 7, 11, 15],
[2, 5, 8, 12, 19],
[3, 6, 9, 16, 22],
[10, 13, 14, 17, 24],
[18, 21, 23, 26, 30]
]
Given target = 5, return true.
Given target = 20, return false.
Python
# time O(m) + O(n)
# matrix[:,end]< target,则该row所有元素均小于target
# matrix[:,end] > target, 则搜索该row 可能发现target
# 从右上角开始搜
class Solution(object):
def searchMatrix(self, matrix, target):
"""
:type matrix: List[List[int]]
:type target: int
:rtype: bool
"""
if matrix:
m = len(matrix)
n = len(matrix[0])
r = 0
c = n - 1
while r < m and c >= 0:
if matrix[r][c] == target:
return True
if matrix[r][c] > target:
c -= 1
else:
r += 1
return False
