• Bubble Sort

  Walk through the simplest sorting algorithm: scan the array, swap adjacent out-of-order pairs, repeat until a full pass has no swaps.

• Climb Stairs

  Count the distinct ways to climb n stairs taking 1 or 2 steps at a time. The recursion explores every path and counts the leaves.

• Elapsed Minutes

  Add up the real minutes between clock readings, even when the clock falls back an hour.

• First Drop

  For each day, scan forward to find the next day whose temperature drops by at least the given threshold; uses a reverse-iteration BST so every node in the tree is a future day.

• Fulfilled Orders Before Failure

  Process an order queue against a freezer of flavors. Each order consumes one of each listed flavor; the first order that asks for an empty slot stops the line.

• Get Sundays

  Walk day-by-day through a month (located via Zeller's congruence) and collect every Sunday as a Y-M-D string.

• Ghostwriter

  A ghost types a word one key at a time: '#' erases the last letter and '~' echoes it. What ends up on the page?

• Longest Sorted

  Find the longest word in a sentence whose letters appear in alphabetical order (e.g. "almost").

• Max Candy

  Collect the most candy from a row of houses without visiting two adjacent ones.

• Min Moves

  Rotate each digit of a 4-dial lock the minimum number of clicks to reach the goal combination, counting both directions and wrapping 9→0 / 0→9.

• Minutes Until Apocalypse

  Each minute, every zombie bites a human neighbour. How long until every human is gone — or until they're walled in forever?

• Pack Rectangles

  Drag wooden rectangles onto the board — fit every piece the algorithm says is possible, rotating as needed.

• Partition Array

  Walk the array once. Send every odd to its bucket, every non-zero even to its bucket, and every zero to its bucket. The result is the three buckets concatenated.

• Quick Sort

  Pick a pivot, partition the array so smaller values go left and larger go right, then recurse on each side. The pivot ends up in its final sorted position after each partition.

• Reorder

  Reorder an array in place by following the destination indices, one cycle at a time.

• Trim

  A project where you have to trim the blank spaces from a string at the leading, trailing, or both. With a nice visualization inspired by the Pacman video game, the pacman will gladly eat those white spaces for you.

▸ no challenges match your search