Algorithm visualizer

See every step, with your own input

Pick an algorithm, enter your own numbers or use a preset, then step through the run. The pseudocode and the explanation follow each step.

Arrays and searching

Sorting

Stacks, queues and Fenwick tree

Trees and tries

Graphs

Dynamic programming

Greedy and backtracking

Fenwick tree (binary indexed tree)

Store block sums so a prefix sum or a point change touches only about log n cells. Each index covers the block of values below its lowest set bit.

Add 1 at index 1 and then query 8. Which cells did the query add, and why those cells?

Step 1 of 29

Index 0 is unused. Build the tree by adding each value at its own index.

Speed

Labels under values name their role, such as lo, hi, mid, i, j, min, L and R. Faded items are already ruled out or already in place.

Fenwick tree (binary indexed tree)

Store block sums so a prefix sum or a point change touches only about log n cells. Each index covers the block of values below its lowest set bit.