题目
Write an efficient algorithm that searches for a value target
in an m x n
integer matrix 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.
Example 1:
Input: 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]], target = 5
Output: true
Example 2:
Input: 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]], target = 20
Output: false
Constraints:
m == matrix.length
n == matrix[i].length
1 <= n, m <= 300
-109 <= matrix[i][j] <= 109
- All the integers in each row are sorted in ascending order.
- All the integers in each column are sorted in ascending order.
-109 <= target <= 109
思路
初始化指针在矩阵的左下方,当当前元素比目标数值大时,上移一格;当比目标数值小时,右移一格;直至相等。
代码
python版本:
class Solution:
def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
l, r = len(matrix)-1, 0
while 0 <= l < len(matrix) and 0 <= r < len(matrix[0]):
if matrix[l][r] > target:
l -= 1
elif matrix[l][r] < target:
r += 1
else:
return True
return False