Form a Chemical Bond - Practice Coding Problems

Form a Chemical Bond - Problem

Database Easy

🧪 Chemical Bonding Lab Challenge

You're working in a chemistry lab and need to determine which elements can form ionic bonds! In chemistry, ionic bonds form when electrons are transferred between atoms - specifically when a Metal (which donates electrons) pairs with a Nonmetal (which accepts electrons).

Given a database table Elements containing information about different chemical elements:

Column Name	Type
symbol	varchar
type	enum ('Metal', 'Nonmetal', 'Noble')
electrons	int

Rules:

🥇 Noble gases are chemically inert (electrons = 0) and don't form bonds
⚡ Metals can give electrons (positive electron value)
🔋 Nonmetals can accept electrons (positive electron value represents need)
💫 Bond formation: Only Metal + Nonmetal pairs can form ionic bonds

Your task is to find all possible element pairs that can form chemical bonds and return them in a result table.

Input & Output

example_1.sql — Basic Elements

$ Input: Elements table: | symbol | type | electrons | |--------|----------|----------| | Na | Metal | 1 | | Cl | Nonmetal | 1 | | He | Noble | 0 |

› Output: | metal | nonmetal | |-------|----------| | Na | Cl |

💡 Note: Na (Metal) can form a bond with Cl (Nonmetal). He (Noble gas) cannot form bonds, so it's not included in any pairs.

example_2.sql — Multiple Elements

$ Input: Elements table: | symbol | type | electrons | |--------|----------|----------| | Li | Metal | 1 | | Na | Metal | 1 | | F | Nonmetal | 1 | | Cl | Nonmetal | 1 | | Ar | Noble | 0 |

› Output: | metal | nonmetal | |-------|----------| | Li | Cl | | Li | F | | Na | Cl | | Na | F |

💡 Note: Each metal (Li, Na) can bond with each nonmetal (F, Cl), creating 4 possible bonds. Ar (Noble) forms no bonds.

example_3.sql — Edge Case

$ Input: Elements table: | symbol | type | electrons | |--------|----------|----------| | He | Noble | 0 | | Ne | Noble | 0 |

› Output: | metal | nonmetal | |-------|----------|

💡 Note: No bonds possible since there are only Noble gases, which are chemically inert and don't form ionic bonds.

Visualization

Tap to expand

Understanding the Visualization

Separate by Type

Group elements into Metals (electron donors), Nonmetals (electron acceptors), and Noble gases (inert)

Apply Bonding Rules

Only Metals and Nonmetals can form ionic bonds through electron transfer

Generate All Combinations

Create every possible Metal-Nonmetal pair using cross join

Output Bond Pairs

Return the complete list of elements that can form chemical bonds

Key Takeaway

🎯 Key Insight: Ionic bonds form through electron transfer between metals (which lose electrons) and nonmetals (which gain electrons). The optimal SQL solution filters elements by type first, then uses a cross join to efficiently generate all valid Metal-Nonmetal combinations.

Time & Space Complexity

Time Complexity

⏱️

O(m × n)

Where m is number of metals and n is number of nonmetals

✓ Linear Growth

Space Complexity

O(m × n)

Result set contains exactly m × n valid bond combinations

⚡ Linearithmic Space

Constraints

1 ≤ number of elements ≤ 1000
Element symbols are unique and 1-2 characters long
type is one of: 'Metal', 'Nonmetal', 'Noble'
electrons = 0 if and only if type = 'Noble'
electrons ≥ 0 for all elements

Asked in

G Google 12 a Amazon 8 ⊞ Microsoft 6 O Oracle 15

The optimal approach uses a filtered cross join to directly combine metals with nonmetals. Instead of generating all possible element pairs and then filtering, we filter first (selecting only metals and nonmetals) and then join the filtered subsets. This eliminates unnecessary combinations and provides better performance with O(m×n) complexity where m = metals, n = nonmetals.

Common Approaches

Approach	Time	Space	Notes
✓ Optimized Join (Best Approach)	O(m × n)	O(m × n)	Directly join metals with nonmetals using filtered cross join
Brute Force (Self Join)	O(n²)	O(n²)	Check every possible pair of elements using self join

Optimized Join (Best Approach) — Algorithm Steps

Filter Elements table to get only Metals
Filter Elements table to get only Nonmetals
Cross join the filtered Metal and Nonmetal subsets
Return all metal-nonmetal symbol pairs

Visualization

Tap to expand

Step-by-Step Walkthrough

Filter Metals

Extract all Metal type elements into subset

Filter Nonmetals

Extract all Nonmetal type elements into subset

Cross Join Subsets

Combine only Metal × Nonmetal combinations

Generate Bonds

Output optimized result with only valid pairs

Code -

solution.c — C

-- Optimized SQL Solution for Chemical Bonding
-- Most efficient approach

SELECT 
    m.symbol AS metal,
    n.symbol AS nonmetal
FROM Elements m
JOIN Elements n ON m.type = 'Metal' AND n.type = 'Nonmetal'
ORDER BY m.symbol, n.symbol;

Time & Space Complexity

Time Complexity

⏱️

O(m × n)

Where m is number of metals and n is number of nonmetals

✓ Linear Growth

Space Complexity

O(m × n)

Result set contains exactly m × n valid bond combinations

⚡ Linearithmic Space

Constraints

1 ≤ number of elements ≤ 1000
Element symbols are unique and 1-2 characters long
type is one of: 'Metal', 'Nonmetal', 'Noble'
electrons = 0 if and only if type = 'Noble'
electrons ≥ 0 for all elements

28.4K Views

Medium Frequency

~8 min Avg. Time

892 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

🧪 Chemical Bonding Lab Challenge

Input & Output

Visualization

Time & Space Complexity

Related Problems

Constraints

Common Approaches

Optimized Join (Best Approach) — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Constraints

Select Compiler