Array | Sorting

Sorting an array means arranging the elements of the array in a certain order. Generally sorting in an array is done to arrange the elements in increasing or decreasing order.

Important terminologies related to Sorting:

Here we will see several algorithms used for array sorting. But before that let us see some important terminologies related to sorting:

In-Place Sorting: In-place sorting means arranging the elements without using any extra space other than the given array.

Stability of Sorting: A sorting algorithm is said to be stable if the relative order of the same valued elements is preserved in the final sorted array i.e., the relative order of the same valued elements in the sorted array is the same as in the original array.

Some commonly used Array Sorting Algorithms:

Bubble Sort: Bubble Sort is the simplest sorting algorithm that works by repeatedly swapping the adjacent elements if they are in the wrong order. This algorithm is not suitable for large arrays as its average and worst-case time complexity is quite high.

Selection Sort: Selection sort is another sorting technique in which we find the minimum element in every iteration and place it in the array beginning from the first index. Thus, a selection sort also gets divided into a sorted and unsorted subarray.

Insertion Sort: Insertion sort similarly to the way we sort playing cards in our hands. The array is virtually split into a sorted and an unsorted part. Values from the unsorted part are picked and placed in the correct position in the sorted part.

Merge Sort: It is a sorting algorithm that is based on the Divide and Conquer paradigm. In this algorithm, the array is repeatedly divided into two equal halves and then they are combined in a sorted manner.

Quick Sort: This is a sorting algorithm based on the divide and conquer approach where an array is divided into subarrays by selecting a pivot element (element selected from the array).

Heap Sort: Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to the selection sort where we first find the minimum element and place the minimum element at the beginning. Repeat the same process for the remaining elements.

Counting Sort: Counting sort is a sorting technique based on keys between a specific range. It works by counting the number of elements having distinct key values (kind of hashing). Then do some arithmetic to calculate the position of each element in the output sequence.

To learn more about all other types of Sorting Algorithms, refer to the below articles:

• Introduction to Sorting Techniques – Data Structure and Algorithm Tutorials
• Sorting Algorithms

Comparison of Time Complexity of Sorting Algorithms:

Some practice problems on Array Sorting:

• Easy:
  1. Program to check if an array is sorted or not (Iterative and Recursive)
  2. Print sorted distinct elements of array in C++
  3. Print All Distinct Elements of a given integer array
  4. Alternative Sorting
  5. Sort an array in wave form
  6. Sort on the basis of number of factors using STL
  7. Sort an array which contain 1 to n values
  8. Sort 1 to N by swapping adjacent elements
  9. Sort elements by frequency | Set 1
  10. Sort an array containing two types of elements
  11. Sort an array according to absolute difference with given value
  12. Sorting all array elements except one
  13. Minimum product pair an array of positive Integers
  14. Minimum adjacent swaps required to Sort Binary array
  15. Pairs with Difference less than K
• Intermediate:
  1. Sort a nearly sorted (or K sorted) array
  2. Count Inversions in an array | Set 1 (Using Merge Sort)
  3. Union and Intersection of two sorted arrays
  4. Sort an array of 0s, 1s and 2s
  5. Check if reversing a sub array make the array sorted
  6. Merge 3 Sorted Arrays
  7. Sorting array except elements in a subarray
  8. Count all distinct pairs with difference equal to k
  9. Construct an array from its pair-sum array
  10. Ropes left after every removal of smallest
  11. Check if any interval completely overlaps the other
  12. Maximizing Unique Pairs from two arrays
• Hard:
  1. Minimum number of swaps required to sort an array
  2. Find the Minimum length Unsorted Subarray, sorting which makes the complete array sorted
  3. Median in a stream of integers (running integers)
  4. Merge two sorted arrays with O(1) extra space
  5. Minimum De-arrangements present in array of AP (Arithmetic Progression)
  6. Divide an array into k segments to maximize maximum of segment minimums
  7. Maximum number of partitions that can be sorted individually to make sorted
  8. Rank of all elements in an array
  9. Merging two unsorted arrays in sorted order
  10. Sort an array after applying the given equation
  11. Minimum swaps to make two arrays consisting unique elements identical

Quick Links :

• ‘Practice Problems’ on Arrays
• ‘Quizzes’ on Arrays
• ‘Video Tutorials’ on Arrays