Insertion Sort

Hook

Insert a playing card into your already ordered hand by sliding larger cards aside.

Watch

Make room for the next value. Run best, average, worst and seeded random inputs; the animation is a reversible execution trace.

How it works

1. Hold the next key outside the sorted prefix.
2. Shift strictly larger keys one position right.
3. Place the key into the newly opened slot.

Try it

Pause at each decision and predict the operation before revealing its result. Input arrays are limited to 64 bounded integers.

Complexity

A sorted prefix needs one comparison per insertion. Reverse order can shift all earlier keys, giving quadratic work.

Code

Choose a language in the code panel. The highlighted stage follows the trace; counters record the visualized reads, writes, comparisons and swaps.

When to use

Use it for small arrays, nearly sorted inputs and short runs inside hybrid sorts.

Interview pitfalls

Shift only strictly larger keys to preserve stability; do not lose the held key.

Quiz

Test the invariant and complexity below, then compare another algorithm on the same input.