Compilare: main.cpp: In function 'void add_string(const string&)': main.cpp:54:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<to_add.length(); i++) ~^~~~~~~~~~~~~~~~ main.cpp: In function 'int get_ocurences(const string&)': main.cpp:77:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<to_check.length(); i++) ~^~~~~~~~~~~~~~~~~~ main.cpp: In function 'int longest_prefix(const string&)': main.cpp:100:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<input.length(); i++) ~^~~~~~~~~~~~~~~ main.cpp: In function 'void erase_string(const string&)': main.cpp:120:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<to_check.length(); i++) ~^~~~~~~~~~~~~~~~~~ main.cpp:132:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<nodes.size(); i++) ~^~~~~~~~~~~~~