Currently a graduating student that goes to one of those top schools. Do you really wanna know how long many of my peers are studying for these interviews? Months!!!!!
I have a few friends that spent all of last summer after their daily internships doing interview prep for fall recruiting season. I also have a cousin that spent 5-6 months unemployed(given he did a masters/bs in ee and not in cs but wanted to move into the field) doing interview prep and just landed offers from Google and Dropbox. The competition is absolutely ruthless.