Leetcode #194: Transpose File
In this guide, we solve Leetcode #194 Transpose File 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 a text file file.txt, transpose its content. You may assume that each row has the same number of columns, and each field is separated by the ' ' character.
Quick Facts
- Difficulty: Medium
- Premium: No
- Tags: Shell
Intuition
The constraints allow a direct scan that keeps only the essential state.
By translating the requirements into a clean loop, the logic stays easy to reason about.
Approach
Iterate through the data once, updating the state needed to compute the answer.
Return the final state after the traversal is complete.
Steps:
- Parse the input.
- Iterate and update state.
- Return the computed answer.
Example
name age
alice 21
ryan 30
Python Solution
def transpose_file(path: str = "file.txt") -> None:
with open(path, "r", encoding="utf-8") as f:
rows = [line.strip().split() for line in f]
if not rows:
return
cols = len(rows[0])
for c in range(cols):
print(" ".join(row[c] for row in rows))
Complexity
The time complexity is O(n). The space complexity is O(1) to O(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.