Compilare: main.cpp: In function 'void GetVecini(int, char&, char&)': main.cpp:12:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i + 1 == x.length()) v2 = x[0]; ~~~~~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < x.length(); ++i) ~~^~~~~~~~~~~~ main.cpp:24:20: warning: array subscript has type 'char' [-Wchar-subscripts] matrix[x[i]][v1][v2]++; ^ main.cpp:24:24: warning: array subscript has type 'char' [-Wchar-subscripts] matrix[x[i]][v1][v2]++; ^ main.cpp:24:28: warning: array subscript has type 'char' [-Wchar-subscripts] matrix[x[i]][v1][v2]++; ^