Q: What is Big O (time complexity) of finding an element in hash table?
Q: What is Big O (time complexity) of sorting an array?
O(n log n)
I had to look up answers for these two questions. I now (hopefully) understand big O to be a notation used to estimate an algorithm's relationship between the size of its input and its performance (speed in this case but could also be used to estimate disk space or another resource).