Dry Run Whiteboard for LeetCode

Dry-run LeetCode on a whiteboard beside your code: arrays, trees, graphs and pointers drawn from the problem's own examples.

A whiteboard that opens over LeetCode's problem page, made for dry runs. It reads the problem: click "Example 1" and every input is drawn as the right structure (an array, a string, a linked list, a binary tree, a grid, a graph) named after its parameter, with the expected output beside it. Then step through your algorithm with pointers, and a trace table fills itself. DRAWN FROM THE PROBLEM • One click per example, or the Testcase panel with your own edits. • Linked lists with cycles, binary trees from level order, n-ary trees, edge lists, adjacency lists, weighted and directed graphs, design problems as a table of calls. • Change what it became with one click: array, list, tree, grid, graph, text. POINTERS, STEPS AND A TRACE TABLE • Add pointers (i, j, lo, mid, hi, slow, fast…) and walk them with the arrow keys. • Press . for the next step. Every step remembers the values, pointers and marks, so you can go back with , and see exactly what changed. • The trace table fills itself: one row per step, one column per pointer and variable, e.g. "2 (11)". Type over any cell. • Mark cells as current, visited, done, skipped or the answer. Play the steps back one per second. A REAL WHITEBOARD TOO • Pen with pressure, highlighter, shapes, arrows that stick to cells, text and sticky notes, a laser pointer. • The Array tool: drag across for as many boxes as you need. Grids, DP tables with the strings as headers, stacks, queues, maps, sets, bits. • A command bar: type /tree [3,9,20,null,null,15,7], /dp "abcde" "ace", /graph 0-1 1-2. Paste [2,7,11,15] and it becomes an array. BESIDE YOUR CODE • Dock it over the description or over the code, so you can read the problem or write the solution beside your drawing. Or float it, or go full screen. • Glass mode: draw over the whole page, then press Esc. • Highlight the problem statement in three colors. Highlights come back after a reload. • Every problem keeps its own board, saved automatically. • Export a PNG to paste into your notes, or the board as a file. FAST AND PRIVATE • Nothing runs until you open it; the page stays exactly as fast. • No account, no sign-in, no analytics and no network requests. Your boards stay in your browser. Back them up to a file from the popup. • Runs only on problem pages of leetcode.com and leetcode.cn, contests included. Keyboard: Alt+Shift+D opens it (change it at chrome://extensions/shortcuts); press ? on the board for every key. Dry Run Whiteboard for LeetCode is an independent project and is not affiliated with or endorsed by LeetCode.