标签：interview
20.4 Write a method to count the number of 2s between 0 and n.
// What this mean?
// Given a n.
// for (int i = 0 -> n)
// {
// result += numOf2In(i);
// }
// This is purely a math problem.标签：interview
原文地址：http://7371901.blog.51cto.com/7361901/1588556
