Compilare: user.cpp: In function ‘int main()’: user.cpp:53:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ^ user.cpp:59:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<x.size();j++) ^ user.cpp:82:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<u.size();i++) ^ user.cpp:87:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<u.size() && u[i].val==tmp.val) ^ user.cpp:97:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<u.size();j++) ^