expert
12 min read
Maximal Rectangle
Turn each matrix row into a histogram, solve that histogram with a monotonic stack, and keep only the state that can still affect future rows.
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7 articles in this tag.
expert
14 min read
Median of Two Sorted Arrays
Merging is the obvious solution. It is also disqualified by the runtime requirement. The useful reframe is to search for a cut, not for a value: place…
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expert
14 min read
Regular Expression Matching
A greedy scan breaks at * because the pattern can take two legal futures: skip the quantified element, or consume one matching character and keep the same…
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expert
13 min read
Scramble String
The difficult part of the Scramble String solution is not recognizing that characters are rearranged. It is preserving the recursive boundaries that made…
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expert
13 min read
Substring with Concatenation of All Words
Equal-width tokens turn a permutation problem into a finite set of aligned frequency windows.
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expert
14 min read
Sudoku Solver
The phrase “try digits and backtrack” is the easy part. The interview-grade solution keeps four representations synchronized: the board, row constraints,…
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expert
13 min read
Wildcard Matching
The reliable way to solve wildcard matching is to model it as reachability over two consumed prefixes—not as an improvised backtracking fight with *.
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