A
AiTechWorlds
AiTechWorlds
See Counting Sort tally value frequencies and write back in linear O(n+k) time — non-comparison sorting visualized.
def counting_sort(a):
mx = max(a)
count = [0] * (mx + 1)
for x in a: count[x] += 1
idx = 0
for v in range(mx + 1):
while count[v] > 0:
a[idx] = v; idx += 1; count[v] -= 1Counting Sort counts how many times each value occurs, then writes values back in order. It is non-comparison based and runs in linear time when the value range k is small.
| Best | O(n + k) |
| Average | O(n + k) |
| Worst | O(n + k) |
| Space | O(n + k) |
| Stable | Yes |
| In-place | No |
The Counting Sort Visualizer animates how Counting Sort works: it counts how many times each value occurs, then writes the values back in sorted order. It is a non-comparison sort that runs in O(n + k) time, where k is the value range. Counting Sort is stable but needs O(n + k) extra space, so it works best when k is small relative to n.
Generate an array
Click New Array or adjust the size slider for a random dataset of small integers.
Play the animation
Press Play to watch values counted, then written back in order.
Step and scrub
Step forward/back or drag the timeline to follow each write.
Read the synced code
The highlighted pseudocode line tracks the count and output phases; switch tabs for C++, Java, Python, or JavaScript.
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Last reviewed on June 14, 2026 by the AiTechWorlds Tools Team. All processing runs locally in your browser.