Visualizers

Partition around a pivot (last element, Lomuto), then sort both sides. O(n log n) average.

Each step compares the middle element and discards half of the remaining range. Switch to “lower bound” to see the lo < hi template that finds the first index where a condition becomes true.

Every move rules out a whole row or column of candidate pairs, so the search takes O(n) instead of O(n²).

The right edge always moves forward; the left edge moves forward only to restore validity. Both move at most n times → O(n).

Indices wait on the stack until a bigger value arrives and answers them. Each index is pushed and popped once → O(n).

Explores in rings of equal distance. Finds the shortest path by number of steps, but ignores terrain cost. Click or drag on the grid to draw walls or mud (cost 5); every edit re-runs the search.

In-order visits left, root, right. On a BST this yields the values in sorted order. Values are inserted into a binary search tree in the order you type them.

dp[i][j] = LCS length of the first i letters of the row string and the first j letters of the column string. Watch each cell pull from its neighbours, then backtrack to recover the subsequence.