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

Prefix sums: answer range sums in O(1)

Build P, where P[i] is the sum of the first i values. Then the sum of any range [l, r] is P[r+1] - P[l].

Add a query that covers a single index. Confirm that P[r+1] - P[l] gives that one value.

Step 1 of 11

prefix P

new

P[0] = 0. The empty prefix sums to 0.

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.

Prefix sums: answer range sums in O(1)

Build P, where P[i] is the sum of the first i values. Then the sum of any range [l, r] is P[r+1] - P[l].