Letters and Numbers: Find Longest Subarray with Equal Letters and Digits (CTCI 17.5)

TL;DR

• The Problem: CTCI problem 17.5 technical mechanics.
• The Approach: CTCI problem 17.5: find the longest contiguous subarray containing an equal number of letters and numbers in O(N) time.
• Complexity: Optimal Time and Memory bounds.

This article provides a clear breakdown of CTCI problem 17.5.

1. Context and Problem Statement

CTCI problem 17.5: find the longest contiguous subarray containing an equal number of letters and numbers in O(N) time.

2. Technical Code & Mechanics

public static char[] findLongestSubarray(char[] array) {
    int[] deltas = computeDeltaArray(array);
    int[] match = findLongestMatch(deltas);
    return extractSubarray(array, match[0] + 1, match[1]);
}

3. Key Takeaways and Edge Cases

Always test boundary conditions and invalid input states.