Transpose Matrix

LeetCode 898 | Difficulty: Easy

Easy

Problem Description

Given a 2D integer array matrix, return the transpose of matrix.

The transpose of a matrix is the matrix flipped over its main diagonal, switching the matrix's row and column indices.

Example 1:

Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
Output: [[1,4,7],[2,5,8],[3,6,9]]

Example 2:

Input: matrix = [[1,2,3],[4,5,6]]
Output: [[1,4],[2,5],[3,6]]

Constraints:

- `m == matrix.length`

- `n == matrix[i].length`

- `1 <= m, n <= 1000`

- `1 <= m * n <= 10^5`

- `-10^9 <= matrix[i][j] <= 10^9`

Topics: Array, Matrix, Simulation

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Approach

Matrix

Treat the matrix as a 2D grid. Common techniques: directional arrays (dx, dy) for movement, BFS/DFS for connected regions, in-place marking for visited cells, boundary traversal for spiral patterns.

When to use

Grid traversal, island problems, path finding, rotating/transforming matrices.

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Solutions

Solution 1: C# (Best: 320 ms)

Metric	Value
Runtime	320 ms
Memory	N/A
Date	2018-07-11

Solution

public class Solution {
    public int[][] Transpose(int[][] A) {
        int m = A.GetLength(0);
    int n = A[0].GetLength(0);
    int[][] result = new int[n][];
    for (int i = 0; i < n; i++)
    {
        result[i] = new int[m];
    }
for (int j = 0; j < n; j++){
    for (int i = 0; i < m; i++)
    {
        
        
            result[j][i] = A[i][j];
            
        }
        Console.WriteLine();
    }
    return result;
    }
}

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Complexity Analysis

Approach	Time	Space
Solution	$O(n)$	$O(1) to O(n)$

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Interview Tips

Key Points

• Start by clarifying edge cases: empty input, single element, all duplicates.
• LeetCode provides 1 hint(s) for this problem — try solving without them first.

💡 Hints

Hint 1: We don't need any special algorithms to do this. You just need to know what the transpose of a matrix looks like. Rows become columns and vice versa!