搜索二维矩阵 II
Search a 2D Matrix II
题目详情
问题:搜索二维矩阵 II
考察:数组、二分查找、双指针
来源:Citadel
链接:https://www.jointaro.com/interviews/questions/search-a-2d-matrix-ii/
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.lengthn == matrix[i].length1 <= 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
解析
思路:从右上角开始搜索。若当前值大于目标,整列当前以下都更大,向左;若小于目标,整行当前以左都更小,向下。
复杂度:时间 O(m+n),空间 O(1)。