Compilare: user.cpp: In function ‘int main()’: user.cpp:40:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int ii = 0; ii < a.size(); ii++) ~~~^~~~~~~~~~ user.cpp:41:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int jj = 0; jj < a.size(); jj++) ~~~^~~~~~~~~~ user.cpp:44:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int ii = 0; ii < b.size(); ii++) ~~~^~~~~~~~~~ user.cpp:45:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int jj = 0; jj < b.size(); jj++) ~~~^~~~~~~~~~ user.cpp:49:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int ii = 0; ii < a.size(); ii++) ~~~^~~~~~~~~~ user.cpp:50:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int jj = 0; jj < b.size(); jj++) ~~~^~~~~~~~~~ user.cpp:50:9: warning: this ‘for’ clause does not guard... [-Wmisleading-indentation] for (int jj = 0; jj < b.size(); jj++) ^~~ user.cpp:53:11: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘for’ if (meh == 0) ^~