Bubble sort is usually the first sorting algorithm taught because it is a simple sorting algorithm that repeatedly steps through the list to be sorted, compares each pair of adjacent items and swaps them if they are in the wrong order.
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Runtime Complexity (BigO notation)  For array with the size of N items, The algo requires N steps to complete first Pass
but it requires N1 steps for Pass 2.
Similarly, It will take N2 steps for Pass 3 and so on for subsequent passes. So, Using bubble sort, the total number of steps required are: N + (N1) + (N2) + ... ≈ (N * (N1)) / 2 ≈ N² 
Big O efficiency:
