#### Algorithm - Quick reference - 4

16. What is the space complexity of an algorithm ?
In computer science, the space complexity of an algorithm or a computer program is the amount of memory space required to solve an instance of the computational problem as a function of the size of the input. It is the memory required by an algorithm to execute a program and produce output.

17. Explain the difference between stack and queue ?
Stack and Queue both are the non-primitive data structures. The main differences between stack and queue are that stack uses LIFO (last in first out) method to access and add data elements whereas Queue uses FIFO (First in first out) method to access and add data elements.Stack has only one end open for pushing and popping the data elements on the other hand Queue has both ends open for enqueuing and dequeuing the data elements.

18. What is Heapsort?
Heap Sort is one of the best sorting methods being in-place and with no quadratic worst-case running time. Heap sort involves building a Heap data structure from the given array and then utilizing the Heap to sort the array. Heapsort will start by building a max heap. A binary max heap is a nearly complete binary tree in which each parent node is larger or equal to its children. The heap is stored in the same memory in which the original array elements are. Once the heap is formed, it completely replaces the array. After that, we take and remove the first element, restore the heap property, thus reducing the heap size by 1, after which we place the max element at the end of that memory. This is repeated until we empty out the heap, resulting in the smallest element being in the first place.

19. What is Merge sort ?
Merge sort is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the order of equal elements is the same in the input and output. Merge sort is a divide and conquer algorithm

20. What is graph coloring ?
graph coloring is a special case of graph labeling; it is an assignment of labels traditionally called "colors" to elements of a graph subject to certain constraints. In its simplest form, it is a way of coloring the vertices of a graph such that no two adjacent vertices are of the same color; this is called a vertex coloring.

21. What is Radix sort ?
Radix sort is an integer sorting algorithm that sorts data with integer keys by grouping the keys by individual digits that share the same significant position and value (place value). Radix sort uses counting sort as a subroutine to sort an array of numbers.

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