project euler problem 003

largest prime factor

I use C or C++ to solve project euler problems. But I rarely use long long in coding. After I solved 50 to 100 problems, I found long long is necessity. The problem is easy, even one use some kind of  brute force method. One may read the book from CLRS and try some fancy method. 

It is interesting to notice that for most of the project euler problems that require an integer as an answer, number is usually less than 2^64.