feat: add 14 missing high-yield DSA problems

[vivekyadav-3]

Description:

Hey! I've been using this repo to prep for interviews and noticed some patterns that I felt were important but had very few (or zero) problems. So I went through the list carefully and added 14 problems that I think fill real gaps.

I tried not to add random problems — each one is there for a specific reason.

Monotonic Stack — only had 2 problems, and honestly neither of them really teaches the pattern cleanly. Added the 3 problems that every resource (NeetCode, TUF, etc.) uses to explain it:

#496 Next Greater Element I
#739 Daily Temperatures
#84 Largest Rectangle in Histogram
Binary Search on Answer Space — the existing 18 binary search problems all search in a sorted array. This is a completely different idea where you binary search on the answer itself using a feasible() check. Added 3 problems for this:

#875 Koko Eating Bananas
#1011 Capacity To Ship Packages Within D Days
#410 Split Array Largest Sum
Multi-Source BFS — all existing BFS problems start from one node. Multi-source BFS (starting from multiple cells at once) is a separate trick that comes up a lot in grid problems. Added:

#994 Rotting Oranges
#542 01 Matrix
Prefix Sum + Hash Map — the classic O(n) subarray technique using prefixSum[j] - prefixSum[i] = k wasn't represented at all. Added:

#560 Subarray Sum Equals K
#974 Subarray Sums Divisible by K
Union-Find — the 4 existing Union-Find problems are all also tagged BFS/DFS. Added 2 where DSU is clearly the right tool:

#684 Redundant Connection
#547 Number of Provinces
DP — two sub-types were missing despite the big DP section:

#72 Edit Distance (string DP — different recurrence than LCS which is already there)
#518 Coin Change II (number of ways, vs #322 which finds minimum count)

[vivekyadav-3]

Note: company frequency data is estimated since I don't have a LeetCode session token to run the update script. Happy for maintainers to run cron/update_questions.py to pull real values.

[Copilot]

Pull request overview

Adds 14 interview-prep “high-yield” LeetCode problems into the repository’s central question dataset to better cover several missing patterns (Monotonic Stack, binary search on answer space, multi-source BFS, prefix-sum hash map, DSU, and a couple DP staples).

Changes:

• Appended 14 new question entries (ids: 496, 739, 84, 875, 1011, 410, 994, 542, 560, 974, 684, 547, 72, 518) with patterns, difficulty, and company frequency metadata.
• Updated the dataset updated timestamp value.
• Changed two tag strings to use a literal en dash character instead of the JSON escape sequence.

Suppressed comments (1)

src/data/questions.json:7331

• Same issue as above: switching from \u2013 to a literal en dash will be undone by the cron/update_questions.py metadata writer (default json.dump escapes non-ASCII), causing recurring diffs. Prefer a representation that matches the generator, or update the generator to keep Unicode characters unescaped.

        "Array",
        "String",
        "Trie",
        "Sorting",
        "Aho–Corasick Algorithm"
      ],

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[seanprashad]

Is this the correct slug? Based on the question URL, I don't think so: https://leetcode.com/problems/coin-change-ii/description/

[vivekyadav-3]

You're right, my mistake! The correct slug should be coin-change-ii to match the URL. Fixed and pushed — sorry about that!

[seanprashad]

Thanks, I'll look to add these questions in the future after I vet them