dir.cpp: In function 'bool cmp(std::vector<char, std::allocator<char> >, std::vector<char, std::allocator<char> >)': dir.cpp:15: warning: comparison between signed and unsigned integer expressions dir.cpp:15: warning: comparison between signed and unsigned integer expressions dir.cpp:17: warning: comparison between signed and unsigned integer expressions dir.cpp:17: warning: comparison between signed and unsigned integer expressions dir.cpp:19: warning: comparison between signed and unsigned integer expressions dir.cpp: In function 'int main()': dir.cpp:60: warning: comparison between signed and unsigned integer expressions