How do you solve Flip Square Submatrix Vertically on LeetCode?

Flip Square Submatrix Vertically (LeetCode #3643) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(k) time complexity and O(1) space complexity. Key insight: Flipping a submatrix is similar to reversing an array.

What is the time complexity of Flip Square Submatrix Vertically?

The optimal solution for Flip Square Submatrix Vertically runs in O(k) time and uses O(1) space. The complexity is O(k) since we only iterate through half of the k rows to perform the swaps.

What is the brute force solution for Flip Square Submatrix Vertically?

The brute force approach for Flip Square Submatrix Vertically is Brute Force, with O(n²) time complexity and O(1) space complexity. We can simply reverse the rows of the specified submatrix by iterating through it and swapping rows. This is straightforward but not the most efficient. The optimal Optimal Solution approach improves this to O(k).

What algorithm or data structure is used to solve Flip Square Submatrix Vertically?

Flip Square Submatrix Vertically uses the following concepts: Array, Two Pointers, Matrix. The recommended patterns to study are: Array, Matrix Manipulation.

What are the interview tips for Flip Square Submatrix Vertically?

Explain your thought process clearly. Consider edge cases before coding. Practice similar problems to build confidence.

What are common mistakes when solving Flip Square Submatrix Vertically?

Forgetting to limit swaps to half the rows. Not considering edge cases with small matrices.

#3643

Flip Square Submatrix Vertically

Easy

ArrayTwo PointersMatrixArrayMatrix Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(k)
Space	O(1)	O(1)

💡

Intuition

Time O(k)Space O(1)

Using two pointers, we can efficiently swap rows in the submatrix without needing extra space. This reduces unnecessary iterations.

⚙️

Algorithm

3 steps

1Step 1: Initialize two pointers, one at the top of the submatrix and one at the bottom.
2Step 2: Swap the rows pointed by the two pointers for the specified columns.
3Step 3: Move the pointers towards the center until they meet.

solution.py4 lines

1def flipSubmatrix(grid, x, y, k):
2    for i in range(k // 2):
3        grid[x + i], grid[x + k - 1 - i] = grid[x + k - 1 - i], grid[x + i]
4    return grid

ℹ

Complexity note: The complexity is O(k) since we only iterate through half of the k rows to perform the swaps.

1Flipping a submatrix is similar to reversing an array.
2Two pointers can optimize the swapping process.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.