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

Two pointers: pair with a target sum

On a sorted array, move one pointer from each end. A sum that is too small moves the left pointer right; too large moves the right pointer left.

Precondition: The array must be sorted from smallest to largest.

Make the array longer and find the target sum by hand before stepping. Does your pair match the first one found?

Step 1 of 7

Set i = 0 and j = 5, the two ends of the sorted array.

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.

Two pointers: pair with a target sum

On a sorted array, move one pointer from each end. A sum that is too small moves the left pointer right; too large moves the right pointer left.

Precondition: The array must be sorted from smallest to largest.