1. Left boundary
start marks the left edge that still needs checking.
let start = 0Typorithm · medium
Cocktail Shaker Sort
▷ Interactive algorithm labcocktail-shaker-sortsortingbubble-sortbidirectionalquadratic-time
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Step 1 of 8 · intro card
Learn Cocktail Shaker Sort
Sorting Algorithms
Cocktail Shaker Sort is a bidirectional Bubble Sort: one pass moves large values right, the next moves small values left.
The algorithm keeps both a left boundary and a right boundary.
A forward pass compares neighbors and pushes a large value toward the right side.
A backward pass compares neighbors in reverse and pulls a small value toward the left side.
If a full pass has no swaps, the algorithm exits early.
It is still O(n^2), but it can handle values misplaced in both directions more visibly than Bubble Sort.
Preparing algorithm lab…
01
Scan forward, then backward.
02
Shrink both boundaries.
03
Use swapped for early exit.
04
Adjacent swaps make it stable.
05
Worst-case time remains O(n^2).
function cocktailShakerSort(arr) {
let start = 0;
let end = arr.length - 1;
let swapped = true;
while (swapped) {
swapped = false;
for (let i = start; i < end; i++) {
if (arr[i] > arr[i + 1]) {
[arr[i], arr[i + 1]] = [arr[i + 1], arr[i]];
swapped = true;
}
}
if (!swapped) break;
swapped = false;
end--;
for (let i = end - 1; i >= start; i--) {
if (arr[i] > arr[i + 1]) {
[arr[i], arr[i + 1]] = [arr[i + 1], arr[i]];
swapped = true;
}
}
start++;
}
return arr;
}Read the implementation
Connect each part of the code to the concept before you type.
2. Right boundary
end marks the right edge that still needs checking.
let end = arr.length - 13. Swap flag
The flag keeps passes going only while swaps happen.
let swapped = true4. Forward pass
Move large values right, like Bubble Sort.
for (let i = start; i < end; i++)5. Swap neighbors
Swap adjacent values that are out of ascending order.
[arr[i], arr[i + 1]] = [arr[i + 1], arr[i]]6. Early exit
If the forward pass made no swaps, the array is sorted.
if (!swapped) break7. Shrink right
The largest unsorted value is now fixed at the right edge.
end--8. Backward pass
Move small values left by scanning backward.
for (let i = end - 1; i >= start; i--)9. Grow left
The smallest unsorted value is now fixed at the left edge.
start++A complete learning loop
01
Understand
Read the concept map and follow the code breakdown.
02
Reconstruct
Type the implementation, repair mistakes and work through every recall exercise.
03
Verify
Use the final check without hints; revisit weak concepts in short practice sessions.