Tony's Log

摘要： Not hard to know it is simply transform from in-order to post-order.My first idea is to build a tree from in-order string and then traverse the tree by post-order - naive so slow.Subtle stack manipulation solves it - stack only for operators:http://cs.nyu.edu/courses/Fall12/CSCI-GA.1133-002/notes/In 阅读全文

摘要： Counting trailing 0s of n! It is not very hard to figure out how to count it - simply count how many 5s. Since even numbers are always more than 5s, we don't have to consider even numbers.But counting 5, is tricky. Naive method is quite slow - I got 12+s for 1000000000. And after reading below a 阅读全文