We have already done tutorial on Merge Sort and a tutorial on Heap Sort (Array Based) with both having a time complexity of O(n*log n). Here is another algorithm which has a time complexity of O(n*log n) and it's called QuickSort.
QuickSort as we all know has a similar approach to Merge Sort i.e. it uses Divide-and-Conquer recursive algorithm to sort the values. The difference being is it's an in-place sorting algorithm.
Basically an in-place algorithm is one which transforms the input using a data structure with a small, constant amount of extra storage space.