Compilare: user.cpp:9:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^ user.cpp: In function ‘int main()’: user.cpp:13:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j,k,i=s.size()/2; i<s.size(); i++) ^ user.cpp:17:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (;j>=0 && k<s.size(); j--,k++) ^ user.cpp:19:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k==s.size()) ^ user.cpp:26:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (s[q]!=s[x+1] && x+1<s.size()) q++; ^