Compilare: user.cpp: In function ‘int main()’: user.cpp:22:14: warning: array subscript has type ‘char’ [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ user.cpp:22:17: warning: array subscript has type ‘char’ [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ user.cpp:22:26: warning: array subscript has type ‘char’ [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ user.cpp:22:29: warning: array subscript has type ‘char’ [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^