WAP

http://blog.youkuaiyun.com/bigheadzzy/article/details/8072551

http://blog.youkuaiyun.com/liuyan731/article/details/50403949

http://blog.youkuaiyun.com/evanstudying/article/details/21116431

String, Stack APIs
linux系统 codeblocks
Stack and DP
1. Print all the LCS between two strings.
Variation: remove duplicates
2. Print all the permutations of the string.
Variation: remove duplicates, and change order such that small letters are considered before Capital letters. a->A->b->B->...->z->Z. (Not sure about it, was either this or A->a->B->b..->Z->z)