Compilare: main.cpp: In constructor 'PalTree::PalTree(const string&, const string&)': main.cpp:46:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) ~~^~~~~~~~~~ main.cpp:60:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i < a.size()) ~~^~~~~~~~~~ main.cpp:70:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i < a.size()) ~~^~~~~~~~~~