Compilare: main.cpp: In function 'bool valid(int, std::__cxx11::string)': main.cpp:14:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<s.size(); i++) ~^~~~~~~~~ main.cpp:18:1: warning: this 'if' clause does not guard... [-Wmisleading-indentation] if(v[rf-'a'].end()-p<k) ^~ main.cpp:21:9: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if' advance(p,k); ^~~~~~~