Patients With a Condition - Practice Coding Problems

Patients With a Condition - Problem

Database Easy

You're working as a data analyst for a hospital's electronic health records system. The hospital maintains a Patients table that stores patient information including their medical conditions.

Your task is to identify all patients who have been diagnosed with Type I Diabetes. In the hospital's coding system, Type I Diabetes conditions always start with the prefix DIAB1.

The conditions column contains medical condition codes separated by spaces. For example, a patient might have conditions like "SADIAB100 MYOP" or "DIAB1 MYOP SLEEP".

Goal: Write a SQL query to find the patient_id, patient_name, and conditions of patients with Type I Diabetes.

Key Challenge: The DIAB1 prefix must be at the beginning of a condition code, not embedded within another code. For instance, "SADIAB100" should NOT match, but "DIAB1" or "DIAB100" should match.

Input & Output

example_1.sql — Basic Type I Diabetes Cases

› Output: +------------+--------------+--------------+ | patient_id | patient_name | conditions | +------------+--------------+--------------+ | 1 | Daniel | DIAB1 MYOP | | 3 | Bob | DIAB100 MYOP | +------------+--------------+--------------+

💡 Note: Daniel has 'DIAB1' at the start of conditions, and Bob has 'DIAB100' which also starts with 'DIAB1'. Alice has no DIAB1-related conditions.

example_2.sql — Edge Case with Embedded DIAB1

› Output: +------------+--------------+--------------+ | patient_id | patient_name | conditions | +------------+--------------+--------------+ | 5 | Eve | MYOP DIAB1 | | 6 | Frank | DIAB1 | +------------+--------------+--------------+

💡 Note: Charlie's 'SADIAB100' contains 'DIAB1' but not at the start of a condition code, so it's excluded. Eve has 'DIAB1' after a space (valid), and Frank has 'DIAB1' as the only condition (valid).

example_3.sql — Multiple DIAB1 Conditions

› Output: +------------+--------------+------------------------+ | patient_id | patient_name | conditions | +------------+--------------+------------------------+ | 7 | Grace | DIAB1 HYPER DIAB199 | | 9 | Ivy | DIAB199 HYPER DIAB1 | +------------+--------------+------------------------+

💡 Note: Grace has both 'DIAB1' and 'DIAB199' (both valid), Ivy has 'DIAB199' at start and 'DIAB1' after space (both valid). Henry has no DIAB1-related conditions.

Constraints

1 ≤ patient_id ≤ 10⁵
patient_name contains only alphabetic characters and spaces
conditions contains only uppercase letters, digits, and spaces
Each condition code is separated by exactly one space
Type I Diabetes conditions always start with DIAB1 prefix

Visualization

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Understanding the Visualization

Database Scan

SQL engine scans through all patient records

Pattern Check

For each record, check if conditions match DIAB1 patterns

Word Boundary

Ensure DIAB1 appears at start or after space

Result Set

Return all matching patients

Key Takeaway

🎯 Key Insight: Word boundary pattern matching ensures medical condition codes are matched precisely, preventing dangerous false positives in healthcare data analysis.

Asked in

a Amazon 45 ⊞ Microsoft 32 G Google 28 f Meta 18

The optimal solution uses precise pattern matching with either REGEXP '^DIAB1|\sDIAB1' or LIKE 'DIAB1%' OR LIKE '% DIAB1%' to ensure DIAB1 only matches at word boundaries - either at the start of the conditions string or immediately after a space character. This avoids false positives while correctly identifying all Type I Diabetes patients.

Common Approaches

Approach	Time	Space	Notes
✓ Precise Pattern Matching (Optimal)	O(n*m)	O(1)	Use REGEXP or multiple LIKE patterns to match DIAB1 only at word boundaries
Basic Pattern Matching	O(n*m)	O(1)	Use simple LIKE pattern to match DIAB1 anywhere in conditions

Precise Pattern Matching (Optimal) — Algorithm Steps

Check if conditions string starts with 'DIAB1'
Check if conditions string contains ' DIAB1' (space + DIAB1)
Return patients where either condition is true
Use REGEXP for more elegant pattern matching where supported

Visualization

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Step-by-Step Walkthrough

Check Start Pattern

Match 'DIAB1%' - conditions starting with DIAB1

Check Word Boundary

Match '% DIAB1%' - DIAB1 after space

Combine Results

Union of both patterns gives accurate results

Code -

solution.c — C

// SQL query - Method 1: Using REGEXP
char* query1 = """
SELECT patient_id, patient_name, conditions 
FROM Patients 
WHERE conditions REGEXP '^DIAB1|\\sDIAB1'
""";

// Method 2: Using LIKE patterns
char* query2 = """
SELECT patient_id, patient_name, conditions 
FROM Patients 
WHERE conditions LIKE 'DIAB1%' OR conditions LIKE '% DIAB1%'
""";

Time & Space Complexity

Time Complexity

⏱️

O(n*m)

Where n is number of patients and m is average length of conditions string for pattern matching

✓ Linear Growth

Space Complexity

O(1)

No additional space needed beyond result set

✓ Linear Space

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Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Precise Pattern Matching (Optimal) — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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