Compilare: user.cpp: In function ‘int main()’: user.cpp:101:160: warning: operation on ‘mat[(xa + -1)][(ya + -1)]’ may be undefined [-Wsequence-point] = mat[xa + 2][ya] = mat[xa][ya - 2] = mat[xa][ya + 2] = mat[xa - 1][ya - 1] = mat[xa + 1][ya - 1] = mat[xa + 1][ya + 1] = mat[xa - 1][ya - 1] = -1; ^ user.cpp:153:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 0; i <= ans.size() - 1; ++ i) ^