Quick Sort is an n log n sort. On average it takes O(n log n) time to sort the given list. Quick Sort is usually implemented as an in-place sorting algorithm. The disadvantage with Quick Sort is that in the worst case Quick Sort only gives a quadratic time perfromance ( O(n2) ). This happens when the list to be sorted is already sorted. But on average Quick Sort slightly outperforms both Merge Sort and Heap Sort.