Patients With a Condition - Practice Coding Problems

Patients With a Condition - Problem

Database Easy

You are given a table Patients containing information about hospital patients. Each patient has a unique patient_id, a patient_name, and a conditions column that contains medical condition codes separated by spaces.

Your task: Find all patients who have Type I Diabetes. Type I Diabetes codes always start with the prefix DIAB1.

Return the patient_id, patient_name, and conditions for these patients in any order.

Table Schema

Patients

Column Name	Type	Description
`patient_id` PK	int	Primary key, unique identifier for each patient
`patient_name`	varchar	Full name of the patient
`conditions`	varchar	Medical condition codes separated by spaces (can be empty)

Primary Key: patient_id

Note: The conditions column contains 0 or more condition codes separated by spaces

Input & Output

Example 1 — Mixed Conditions

Input Table:

patient_id	patient_name	conditions
1	Daniel	YFEV COUGH
2	Alice
3	Bob	DIAB100 MYOP
4	George	ACNE DIAB100
5	Alain	DIAB201

Output:

patient_id	patient_name	conditions
3	Bob	DIAB100 MYOP
4	George	ACNE DIAB100
5	Alain	DIAB201

💡 Note:

Patients Bob, George, and Alain have conditions starting with DIAB1. Bob has DIAB100 at the start, George has DIAB100 after a space, and Alain has DIAB201. Daniel and Alice don't have any Type I Diabetes conditions.

Example 2 — Edge Cases

Input Table:

patient_id	patient_name	conditions
1	John	DIAB1
2	Jane	XDIAB100
3	Mike

Output:

patient_id	patient_name	conditions
1	John	DIAB1

💡 Note:

Only John matches because his condition starts with exactly DIAB1. Jane's XDIAB100 doesn't match because DIAB1 is not at the beginning of a word. Mike has no conditions.

Constraints

1 ≤ patient_id ≤ 100000
patient_name consists of uppercase and lowercase letters and spaces
conditions consists of uppercase letters and spaces, separated by single spaces
Type I Diabetes conditions always start with DIAB1 prefix

Visualization

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Understanding the Visualization

Input

Patients table with condition codes

Filter

Match DIAB1 prefix patterns

Output

Patients with Type I Diabetes

Key Takeaway

🎯 Key Insight: Use LIKE with multiple patterns to match prefixes at word boundaries in space-separated strings

Asked in

A Amazon 15 G Google 8 M Microsoft 12

Use LIKE pattern matching with 'DIAB1%' and '% DIAB1%' to find conditions that start with DIAB1 at word boundaries.

Table Schema

Patients

Column Name	Type	Description
`patient_id` PK	int	Primary key, unique identifier for each patient
`patient_name`	varchar	Full name of the patient
`conditions`	varchar	Medical condition codes separated by spaces (can be empty)

Primary Key: patient_id

Note: The conditions column contains 0 or more condition codes separated by spaces

Common Approaches

Approach	Time	Space	Notes
✓ Pattern Matching with LIKE	O(n × m)	O(1)	Use LIKE with wildcards to match DIAB1 prefix at word boundaries

Pattern Matching with LIKE — Algorithm Steps

Step 1: Use WHERE clause with LIKE to match patterns
Step 2: Check for DIAB1 at start of string OR after a space
Step 3: Select required columns for matching patients

Visualization

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Step-by-Step Walkthrough

Scan

Check each patient's conditions

Match

Find DIAB1 at start or after space

Select

Return matching patients

Code -

solution.c — C

Time & Space Complexity

Time Complexity

⏱️

O(n × m)

n patients × m average condition string length for pattern matching

✓ Linear Growth

Space Complexity

O(1)

No additional space needed for pattern matching

✓ Linear Space

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Smart Actions

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Table Schema

Input & Output

Constraints

Visualization

Related Problems

Table Schema

Common Approaches

Pattern Matching with LIKE — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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