Google Intern interview questions

First Interview: Simple questions: Write a program to find a character (and it's occurrence count) in a string. Scale for a paragraph, to a file that doesn't fit in memory to a large set of files split across a network that don't fit in memory of a single machine. Second Interview: Median finding algorithm - find the median of 'n' numbers and a little bit of binary search tree implementation

How many places are there on the earth that one could walk one mile south, then one mile east, then one mile north and end up in the same spot?