Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:26:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < xs.size(); ++i) { ^ user.cpp:30:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < ys.size(); ++i) { ^ user.cpp:37:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < xs.size(); ++i) { ^ user.cpp:49:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < ys.size(); ++i) { ^ user.cpp:34:7: warning: variable ‘startXIdx’ set but not used [-Wunused-but-set-variable] int startXIdx = 0; ^ user.cpp:45:7: warning: variable ‘startYIdx’ set but not used [-Wunused-but-set-variable] int startYIdx = 0; ^