1. Active stack size
Each pass places the maximum of the active prefix at size - 1.
for (let size = arr.length; size > 1; size--)Typorithm · medium
Pancake Sort
▷ Interactive algorithm labpancake-sortsortingprefix-reversalselectionquadratic-time
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Full lesson · 8 learning steps Open any exercise for focused practice
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Step 1 of 8 · intro card
Learn Pancake Sort
Sorting Algorithms
Pancake Sort repeatedly uses prefix reversals to move the largest active value into place.
The only operation in Pancake Sort is flipping a prefix of the array.
Each pass scans the active prefix to find its largest value.
One flip brings that value to the front; another flip moves it to the end of the active prefix.
The active size shrinks because the largest value is now fixed in the sorted tail.
The algorithm is educational and constraint-driven, with O(n^2) time.
Preparing algorithm lab…
01
Find the max in the active prefix.
02
Flip max to the front.
03
Flip max into final position.
04
Shrink the active size.
05
Uses prefix reversals instead of arbitrary swaps.
function pancakeSort(arr) {
for (let size = arr.length; size > 1; size--) {
let maxIndex = 0;
for (let i = 1; i < size; i++) {
if (arr[i] > arr[maxIndex]) {
maxIndex = i;
}
}
if (maxIndex === size - 1) continue;
flip(arr, maxIndex);
flip(arr, size - 1);
}
return arr;
}
function flip(arr, end) {
let start = 0;
while (start < end) {
[arr[start], arr[end]] = [arr[end], arr[start]];
start++;
end--;
}
}Read the implementation
Connect each part of the code to the concept before you type.
2. Max candidate
Start by assuming the active prefix begins with the largest value.
let maxIndex = 03. Find max
Scan only the active unsorted prefix.
for (let i = 1; i < size; i++)4. Update max
Remember where the largest active value is.
maxIndex = i5. Already placed
If the largest active value is already at the end, no flips are needed.
if (maxIndex === size - 1) continue6. Bring max to top
Flip the max value to the front of the array.
flip(arr, maxIndex)7. Place max
Flip it from the front into its final active end position.
flip(arr, size - 1)8. Reverse prefix
The helper reverses values from index 0 through end.
while (start < end)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.