Compilare: user.cpp: In function ‘bool empt(std::vector<int>)’: user.cpp:10:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1;i<viz.size();i++) if (viz[i]==0) return false; ^ user.cpp: In function ‘void heapify(std::vector<int>&, int)’: user.cpp:18:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (2*i+1<x.size() && c[x[i]]>c[x[i*2+1]]) ^ user.cpp:25:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] else if (2*i+2<x.size() && c[x[i]]>c[x[i*2+2]]) ^ user.cpp: In function ‘int main()’: user.cpp:79:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<v[1].size();i++) ^ user.cpp:91:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<v[u].size();i++) ^