Interview 1

[joshyoon92]

Interview 1 on June 7th. 2026

[super30admin]

Interview Problem: Find Missing Number in a sorted array (Problem1.java)

• Strengths: Good attempt at using binary search, correct time and space complexity analysis
• Areas for Improvement:
  1. Fix the syntax error: method signature should be public static int binarySearch
  2. The algorithm should find the missing number without requiring a target value
  3. The logic needs to identify where the array values deviate from their expected indices
  4. Consider edge cases: missing number at the beginning, middle, or end of array
  5. The return value should be the missing number itself, not an index
  6. Test with multiple arrays to ensure correctness

The reference solution correctly identifies the missing number by comparing the difference between array values and their indices, which the student's approach partially captures but doesn't fully implement.

VERDICT: NEEDS_IMPROVEMENT

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Interview Problem: Design Min Heap

Looking at this evaluation, I need to assess the student's solution against the reference solution for implementing a Min Heap.

Problem Understanding:
The problem asks to implement a Min Heap with operations: getMin(), extractMin(), and insert().

Student's Solution Analysis:
The student's code is completely wrong - it's attempting to solve a binary search problem instead of implementing a Min Heap. This is a fundamental mismatch.

Detailed Evaluation:

1. Correctness: FAIL - The student solved a binary search problem instead of implementing a Min Heap. The code doesn't even attempt to create a heap data structure, heapify operations, or any of the required heap methods.

2. Time/Space Complexity: Cannot be evaluated - The solution doesn't implement the required data structure.

3. Code Quality Issues:

   • Wrong problem entirely
   • Syntax error: public return int binarySearch should be public static int binarySearch
   • Logic error: arr[mid] == mid + 1 should be arr[mid] == target
   • The binary search logic is incorrect even for its intended purpose

4. Missing Implementation: No heap class, no insert(), no extractMin(), no getMin(), no heapify, no parent/child helper methods.

Verdict: NEEDS_IMPROVEMENT

The student needs to completely rewrite their solution to actually implement the Min Heap as specified in the problem. They should:

• Create a heap array-based implementation
• Implement proper heapify (sift-down) for removing min
• Implement sift-up for inserting elements
• Include helper methods for parent/left/right child calculations
• Follow the reference solution's structure with proper encapsulation

VERDICT: NEEDS_IMPROVEMENT