Compilare: user.cpp: In function ‘int main()’: user.cpp:20:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i ++) { ~~^~~~~~~~~~ user.cpp:27:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); i ++) { ~~^~~~~~~~~~ user.cpp:32:66: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(fr[c - 'a'] && fr[c - 'a'] + toright[c - 'a'] > s.size() - (i + 1)) { user.cpp:38:35: warning: ‘last’ may be used uninitialized in this function [-Wmaybe-uninitialized] if(nr > 1 || (nr == 1 && s[i] == last)) { ~~~~~~~~~^~~~~~~~~~~~~~~~