3866. First Unique Even Element
We iterate from a manual counts dict through `Counter` to a one-pass dict-as-ordered-set, then land on Counter filtered…
3870. Count Commas in Range
We iterate from an f-string brute-force count to a closed-form one-liner by partitioning the input range. The "partitio…
3875. Construct Uniform Parity Array I
We iterate from a parity case-analysis to a one-line solution. The "prove it's always possible, then return True" patte…
3880. Minimum Absolute Difference Between Two Values
We iterate from a nested-loop pair check to a single-pass scan that only remembers the most recent 1 and 2. The "last-s…
3884. First Matching Character From Both Ends
We iterate from a full-string scan to a half-string walk by noticing the mirror-index symmetry between `s[i]` and `s[n …
3927. Minimize Array Sum Using Divisible Replacements
We iterate from a brute-force pair check through a divisor sieve, then drop the constant factor with numpy. Inverting t…
3894. Traffic Signal Color
We work through an if/elif ladder, then tighten the range checks using Python's chained-comparison syntax. The `a <= x …
3898. Find the Degree of Each Vertex
We sum each row of the adjacency matrix to read off every vertex's degree in one pass. The row-sum-equals-degree identi…
3903. Smallest Stable Index I
We iterate from a brute-force scan to a two-pass sweep that precomputes a right-min array and walks a running left-max.…
3908. Valid Digit Number
We cast the number to a string to check for the digit while guarding against a leading match. The "cast-to-string for d…
3912. Valid Elements in an Array
We iterate from a brute-force scan to a two-pass sweep that walks a running max from each end. The "two-pass running ma…