Leetcode #2480: Form a Chemical Bond
In this guide, we solve Leetcode #2480 Form a Chemical Bond 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
Table: Elements +-------------+---------+ | Column Name | Type | +-------------+---------+ | symbol | varchar | | type | enum | | electrons | int | +-------------+---------+ symbol is the primary key (column with unique values) for this table. Each row of this table contains information of one element.
Quick Facts
- Difficulty: Easy
- Premium: Yes
- Tags: Database
Intuition
The task is relational in nature, which maps cleanly to DataFrame operations in Python.
By treating tables as DataFrames, joins and group-bys become concise and readable.
Approach
Load the inputs as DataFrames and apply the appropriate merge, filter, or group-by.
Select or rename the columns to match the required output.
Steps:
- Load inputs as DataFrames.
- Apply merge/groupby/filter operations.
- Select the output columns.
Example
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| symbol | varchar |
| type | enum |
| electrons | int |
+-------------+---------+
symbol is the primary key (column with unique values) for this table.
Each row of this table contains information of one element.
type is an ENUM (category) of type ('Metal', 'Nonmetal', 'Noble')
- If type is Noble, electrons is 0.
- If type is Metal, electrons is the number of electrons that one atom of this element can give.
- If type is Nonmetal, electrons is the number of electrons that one atom of this element needs.
Python Solution
import duckdb
import pandas as pd
def solution(elements: pd.DataFrame) -> pd.DataFrame:
con = duckdb.connect()
con.register("Elements", elements)
return con.execute("""SELECT a.symbol AS metal, b.symbol AS nonmetal
FROM
Elements AS a,
Elements AS b
WHERE a.type = 'Metal' AND b.type = 'Nonmetal';""").df()
Complexity
The time complexity is O(n log n) (typical). The space complexity is 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.