Array / String

Trace every profitable upward price edge and accumulate unlimited transaction profit.

Array / String / Greedy Profit

Scan prices once, keep the cheapest buy day seen so far, and evaluate every later day as a possible sell.

Array / String / Greedy Profit

Distribute the fewest candies by enforcing rating inequalities once from the left and once from the right.

Array / String / Greedy Two-Pass Constraints

Return the first index where the needle appears in the haystack by testing candidate windows left to right.

Array / String / Substring Search / Sliding Alignment

Find the unique start index by combining a global balance check with a local running tank that resets on failure.

Array / String / Greedy Circuit Proof

Sort citations in descending order and locate the largest threshold where citations[i] still supports h = i + 1.

Array / String / Threshold Logic

Replay a full RandomizedSet operation log and watch how the dense array and hashmap cooperate to preserve average O(1) operations.

Array / String / Hashmap + Array

Convert an integer into a Roman numeral by greedily minting the largest denomination that still fits the remaining value.

Array / String / Greedy Denominations / Roman Numerals

Interpret the array as BFS layers: currentEnd closes the current jump window, and farthest builds the next one.

Array / String / Minimum Jump Layers

Keep a single farthest-reachable frontier and decide whether the last index ever becomes reachable.

Array / String / Greedy Frontier

Return the length of the last word in a string by scanning from the end, trimming spaces, and counting the final non-space stretch.

Array / String / Reverse Scan / Whitespace

Find the longest shared prefix across a list of strings by comparing one character column at a time.

Array / String / Prefix Scan / Column Comparison

Watch Boyer-Moore pair off competing values until the majority element remains as the final survivor.

Array / String / Voting Invariant

Merge two sorted arrays directly into nums1 and watch how the rightmost free slot makes in-place merging safe.

Array / String / In-Place Merge

Compute the product for every index without division by first storing left products and then multiplying in right products.

Array / String / Prefix and Suffix Products

Keep a valid prefix where every value appears at most twice, using the write-2 lookback to block third copies.

Array / String / Bounded Duplicates

Use the sorted order to keep a compact unique prefix and skip repeated values with a single comparison.

Array / String / Sorted Array Prefix

Compact every non-target value into the front of the array and treat the remaining tail as irrelevant.

Array / String / In-Place Filtering

Normalize the input into clean tokens, then rebuild the sentence from the last token back to the first with exactly one space between words.

Array / String / Tokenization / Reverse Assembly

Convert a Roman numeral into an integer by comparing each glyph to its immediate lookahead and turning it into a signed contribution.

Array / String / Roman Numerals / Lookahead

Rotate right by k steps using the classic reverse-all, reverse-front, reverse-back strategy.

Array / String / Reversal Trick

Greedily pack words into each line, distribute the remaining spaces across the gaps, and left-justify the final line.

Array / String / Greedy Packing / Formatting

Count trapped water in one pass by always resolving the shorter side and maintaining left and right boundary maxima.

Array / String / Two-Pointer Boundary Maxima

Route characters through a bouncing row pointer, then read the row buffers back in order to form the zigzag-converted string.

Array / String / Simulation / Zigzag Routing