Description

Given a matrix A, return the transpose of A.

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

Example 1:

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

Example 2:

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

Note:

  1. 1 <= A.length <= 1000
  2. 1 <= A[0].length <= 1000

Solutions

1. Array - Direct

# Time: O(mn)
# Space: O(n)
class Solution:
    def transpose(self, A: List[List[int]]) -> List[List[int]]:
        if not A:
            return []
        row, col = len(A), len(A[0])

        res = []
        for c in range(col):
            cols = []
            for r in range(row):
                cols.append(A[r][c])
            res.append(cols)
        return res

# 36/36 cases passed (76 ms)
# Your runtime beats 56.02 % of python3 submissions
# Your memory usage beats 100 % of python3 submissions (13.5 MB)

References

  1. 867. Transpose Matrix