links.cpp: In function 'bool exit()': links.cpp:17: warning: comparison between signed and unsigned integer expressions links.cpp:22: warning: comparison between signed and unsigned integer expressions links.cpp: In function 'void elim()': links.cpp:46: warning: comparison between signed and unsigned integer expressions links.cpp: In function 'void ref()': links.cpp:56: warning: comparison between signed and unsigned integer expressions links.cpp:67: warning: comparison between signed and unsigned integer expressions links.cpp:53: warning: unused variable 'n' links.cpp:54: warning: unused variable 'it' links.cpp:54: warning: unused variable 'last' links.cpp: In function 'void dfs(std::string)': links.cpp:80: warning: comparison between signed and unsigned integer expressions links.cpp: In function 'int main()': links.cpp:92: warning: comparison between signed and unsigned integer expressions links.cpp:106: warning: comparison between signed and unsigned integer expressions