Compilare: user.cpp: In function ‘int main()’: user.cpp:23:32: warning: operation on ‘x’ may be undefined [-Wsequence-point] y = x ^ y ^ (x = y); ^ user.cpp:43:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v[i].size(); j++) ^ user.cpp:55:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < v[i].size(); j++) ^