Compilare: user.c: In function ‘main’: user.c:14:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] if(fr[s[i]] == 0){ ^ user.c:15:7: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr[s[i]] = 1; ^ user.c:19:11: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr[s[j]]--; ^ user.c:21:9: warning: array subscript has type ‘char’ [-Wchar-subscripts] }while(fr[s[j - 1]] > 0); ^ user.c:26:7: warning: array subscript has type ‘char’ [-Wchar-subscripts] fr[s[i]]++; ^ user.c:10:9: warning: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Wunused-result] fscanf(in, "%d%d ", &n, &k); ^