Quick Sort Algorithm: A Detailed Explanation
Quick sort is a highly efficient sorting algorithm, based on the divide and conquer strategy. It is one of the most widely used algorithms and is known for its performance, simplicity, and versatility. In this blog, we will discuss the quick sort algorithm in detail.
Algorithm:
Choose a pivot element from the array, typically the last element.
Partition the array such that elements smaller than the pivot element are on its left, and elements greater than the pivot element are on its right.
Recursively repeat the above steps on the sub-arrays until the array is sorted.
Step 1: Choose Pivot Element
The pivot element is the key to the quick sort algorithm. It is the element that separates the array into two sub-arrays. The pivot element is typically the last element in the array, but other elements can be chosen as well.
Step 2: Partition the Array
Once the pivot element is chosen, the next step is to partition the array into two sub-arrays. This is done by creating two pointers, one starting from the first element and the other from the second element. The first pointer moves forward and the second pointer moves backward. If the element at the first pointer is greater than the pivot element, the element at the second pointer is swapped with the element at the first pointer. This process continues until the first pointer reaches the second pointer. The pivot element is then swapped with the element at the second pointer.
Step 3: Recursively Repeat the Process
The quick sort algorithm is a recursive algorithm, which means that the process is repeated until the array is sorted. This is done by dividing the array into smaller sub-arrays and repeating the process on each sub-array. The pivot element is chosen from each sub-array, the array is partitioned, and the process is repeated until the array is sorted.
Example:
Let's take an example of an array [10, 80, 30, 90, 40, 50, 70]. The pivot element is chosen as the last element in the array, i.e., 70. The array is partitioned into two sub-arrays, with elements less than 70 on its left and elements greater than 70 on its right. The two sub-arrays are [10, 30, 40, 50] and [80, 90]. The process is repeated on each sub-array until the array is sorted.
Advantages:
Quick sort is a highly efficient algorithm with a time complexity of O(n log n).
It is easy to implement and understand.
It is a versatile algorithm and can be used to sort arrays of any size.
The pivot element can be chosen in many ways, allowing the algorithm to be optimized for different data sets.
Disadvantages:
The performance of the quick sort algorithm can degrade if the pivot element is not chosen optimally.
The algorithm is not as stable as other sorting algorithms such as merge sort.
In conclusion, quick sort is a highly efficient and widely used sorting algorithm. It is simple to understand, implement, and versatile. If the pivot element is chosen optimally, the algorithm can provide an efficient and effective solution for sorting arrays of any size.
