240. Search a 2D Matrix II

Medium (Trung bình) Python 🔗 Xem trên LeetCode

📋 Đề Bài

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

🧠 Thuật Toán & Kỹ Thuật

Matrix (Ma trận)
⏱️ Thời gian O(n)
💾 Không gian O(n)

💻 Lời Giải

Python 0240-search-a-2d-matrix-ii.py 
class Solution:
    def searchMatrix(self, matrix: List[List[int]], target: int) -> bool:
        n, m = len(matrix), len(matrix[0])
        i = 0
        j = m - 1
        
        while i < n and j >= 0:
            if matrix[i][j] == target:
                return True
            elif matrix[i][j] < target:
                i += 1
            else:
                j -= 1
                
        return False