Debug NullPointerException | Dataford Interview Questions

Stack vs. Heap, identifying the cause of a NullPointerException from a code snippet.

Implement find_null_pointer(lines). Each input line models a reference assignment, object allocation, field update, field read, or method call. Return the first null dereference as a zero-based line report, or null if execution completes without one. Variables hold references to heap objects, and missing object fields are treated as null.

Constraints

1 <= lines.length <= 10^4
Each line follows one of the specified statement formats
Variable and field names contain letters, digits, and underscores
Return the first failure using zero-based line numbering
A missing object field evaluates to null

Function Signature

def find_null_pointer(lines):

Your question is Debug NullPointerException. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Stack vs. Heap, identifying the cause of a NullPointerException from a code snippet.

Constraints

1 <= lines.length <= 10^4
Each line follows one of the specified statement formats
Variable and field names contain letters, digits, and underscores
Return the first failure using zero-based line numbering
A missing object field evaluates to null

Function Signature

def find_null_pointer(lines):

Your question is Debug NullPointerException. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.