What are some algorithms which we use daily that have -LSB- math -RSB- O -LRB- n -RRB- , O -LRB- n ^ 2 -RRB- , -LSB- / math -RSB- and -LSB- math -RSB- O -LRB- \ log n -RRB- -LSB- / math -RSB- complexities ?
How is the average case running time of the quick sort algorithm closer to the best case : O -LRB- n log n -RRB- than the worst case : O -LRB- n ^ 2 -RRB- ?