sort in unix

be careful when you use "sort" in unix since it is kind of problematic with the numbers like "9.9591403640072E-4" even if you set "-n".

char * in unordered_map issue

do not use unordered_map<char*,int> map
instead use unordered_map<string, int> map since unordered_map is kind of problematic with pointers

row and col operations in opencv

check out this link before these operations :)

http://docs.opencv.org/modules/core/doc/basic_structures.html#Mat%20Mat%3a%3arow%28int%20y%29%20const


mat.row(1) = mat.row(3) // this does not work!

mat.row(3).copyTo( mat.row(1)) // this works