Leetcode #1886: Determine Whether Matrix Can Be Obtained By Rotation
In this guide, we solve Leetcode #1886 Determine Whether Matrix Can Be Obtained By Rotation in Python and focus on the core idea that makes the solution efficient.
You will see the intuition, the step-by-step method, and a clean Python implementation you can use in interviews.
Problem Statement
Given two n x n binary matrices mat and target, return true if it is possible to make mat equal to target by rotating mat in 90-degree increments, or false otherwise. Example 1: Input: mat = [[0,1],[1,0]], target = [[1,0],[0,1]] Output: true Explanation: We can rotate mat 90 degrees clockwise to make mat equal target.
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: Array, Matrix
Intuition
Grid problems are easiest when you define clear row/column boundaries.
A consistent traversal order prevents off-by-one errors.
Approach
Iterate by rows, columns, or layers depending on the requirement.
Keep bounds updated as the traversal progresses.
Steps:
- Define bounds or directions.
- Visit cells in order.
- Update result and move bounds.
Example
Input: mat = [[0,1],[1,0]], target = [[1,0],[0,1]]
Output: true
Explanation: We can rotate mat 90 degrees clockwise to make mat equal target.
Python Solution
class Solution:
def findRotation(self, mat: List[List[int]], target: List[List[int]]) -> bool:
def rotate(matrix):
n = len(matrix)
for i in range(n // 2):
for j in range(i, n - 1 - i):
t = matrix[i][j]
matrix[i][j] = matrix[n - j - 1][i]
matrix[n - j - 1][i] = matrix[n - i - 1][n - j - 1]
matrix[n - i - 1][n - j - 1] = matrix[j][n - i - 1]
matrix[j][n - i - 1] = t
for _ in range(4):
if mat == target:
return True
rotate(mat)
return False
Complexity
The time complexity is O(m·n). The space complexity is O(1) to O(m·n).
Edge Cases and Pitfalls
Watch for boundary values, empty inputs, and duplicate values where applicable. If the problem involves ordering or constraints, confirm the invariant is preserved at every step.
Summary
This Python solution focuses on the essential structure of the problem and keeps the implementation interview-friendly while meeting the constraints.