Leetcode #2888: Reshape Data: Concatenate
In this guide, we solve Leetcode #2888 Reshape Data: Concatenate 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
DataFrame df1 +-------------+--------+ | Column Name | Type | +-------------+--------+ | student_id | int | | name | object | | age | int | +-------------+--------+ DataFrame df2 +-------------+--------+ | Column Name | Type | +-------------+--------+ | student_id | int | | name | object | | age | int | +-------------+--------+ Write a solution to concatenate these two DataFrames vertically into one DataFrame. The result format is in the following example.
Quick Facts
- Difficulty: Easy
- Premium: No
- Tags: Pandas
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
DataFrame df1
+-------------+--------+
| Column Name | Type |
+-------------+--------+
| student_id | int |
| name | object |
| age | int |
+-------------+--------+
DataFrame df2
+-------------+--------+
| Column Name | Type |
+-------------+--------+
| student_id | int |
| name | object |
| age | int |
+-------------+--------+
Python Solution
import pandas as pd
def concatenateTables(df1: pd.DataFrame, df2: pd.DataFrame) -> pd.DataFrame:
return pd.concat([df1, df2], ignore_index=True)
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.