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Insertion_sort/Readme.md

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+# Insertion Sort
+## Introduction
+
+<p>
+  A simple sorting algorithm which works on the idea of picking elements from the unsorted part one by one and inserting them into their right positions in the sorted part. 
+  The array is virtually divided into 2 parts, a sorted one and an unsorted one. 
+  Just like we arrange a group of shuffled pages according to their page numbers, values from unsorted parts are picked and placed at the right positions in the sorted portion.
+</p>
+
+
+![image](https://user-images.githubusercontent.com/74819092/119613948-538bd700-be1b-11eb-8351-dec8333cb436.png)
+
+* As we can see above, we start from the first 2 elements on the left. Comparing them we know that 3 < 4 so we need to position 3 before 4, so we swap their positions. <br>
+* Next, 2 becomes the key element which we compare with all elements before it until we find something smaller than 2. Since 2 is smaller than both 3 and 4, we place it at the beginning of the array which is its correct position.
+Since 12 is already larger than any element before it, its position is correct (for the current iteration).<br>
+* Finally, comparing 9 with its predecessors, we see it's only smaller than 12 so we swap the positions of 9 and 12 to get the fully sorted array.<br>
+## Algorithm
+For sorting an array of size n in ascending order:
+
+* Start your loop from ```arr[1]``` till ```arr[n]```
+* Compare the selected element of the current iteration (key) to the element before it.
+* If this key is smaller than its predecessor, compare it to the elements before the predecessor.
+* Shift all the greater elements up by one position to make space for the smaller element.
+
+# Complexity Analysis
+n is the number of elements in the array.<br>
+
+## Time Complexity:
+
+Best Case: O (n)<br>
+Average Case: O (n2)<br>
+Worst Case: O (n2)<br>
+Space Complexity: O (1)<br>