Compilare: user.cpp: In function ‘int main()’: user.cpp:39:32: warning: array subscript has type ‘char’ [-Wchar-subscripts] d[i][i + 1] = frec[S[i]][S[i + 1]]; ^ user.cpp:39:42: warning: array subscript has type ‘char’ [-Wchar-subscripts] d[i][i + 1] = frec[S[i]][S[i + 1]]; ^ user.cpp:56:89: warning: array subscript has type ‘char’ [-Wchar-subscripts] d[i][j] = min(d[i][j], d[i + 1][k - 1] + d[k + 1][j] + frec[S[i]][S[k]]); ^ user.cpp:56:95: warning: array subscript has type ‘char’ [-Wchar-subscripts] d[i][j] = min(d[i][j], d[i + 1][k - 1] + d[k + 1][j] + frec[S[i]][S[k]]); ^