Compilare: main.cpp: In function 'int main()': main.cpp:18:18: warning: array subscript has type 'char' [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ main.cpp:18:21: warning: array subscript has type 'char' [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ main.cpp:18:30: warning: array subscript has type 'char' [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^ main.cpp:18:33: warning: array subscript has type 'char' [-Wchar-subscripts] mat[a][b] = mat[b][a] = 1; ^