The Algorithm

Merge Sort is a stable (preserve the order of equal elements), divide and conquer, comparison-based sorting algorithm. It has the worst-case run time of nlogn. The primary disadvantage of merge sort is usage of additional memory space.
The basic idea of merge sort is as below,

Divide the input array into sub [...]

You may want to read the previous post “heap” first.

Heapsort Algorithm

Heapsort is a in-place, not stable, worst-case nlogn sorting algorithm.

The simple implementation of heapsort is simply insert all elements into the heap and then remove the root repeatedly until the heap is empty. This is implemented in the [...]

Brief Notes of the Algorithm
Quicksort has an average run time of nlogn and worst case run time of n^2. Quicksort is often faster than other O(nlogn) algorithms in practice. And it’s used in implementation of C standard library qsort function.

Quicksort is not a stable sort, which means if two elements are equal, [...]