Compilare: user.cpp: In function ‘int main()’: user.cpp:22:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ^ user.cpp:27:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i - k >= 0 && i + k < s.size() && s[i - k] == s[i + k]) { ^ user.cpp:34:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == s.size() - 1 || s[i] != s[i + 1]) continue; ^ user.cpp:37:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i - k >= 0 && i + k + 1 < s.size() && s[i - k] == s[i + k + 1]) { ^