Compilare: user.cpp: In function ‘void add(trie*, int)’: user.cpp:23:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == s.size() ){ ^ user.cpp: In function ‘int del(trie*, int)’: user.cpp:39:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == s.size() ) ^ user.cpp: In function ‘int cuv(trie*, int)’: user.cpp:62:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == s.size() ){ ^ user.cpp: In function ‘int pre(trie*, int)’: user.cpp:77:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (k == s.size() ) ^ user.cpp: In function ‘int main()’: user.cpp:86:9: warning: unused variable ‘n’ [-Wunused-variable] int n, op; ^ user.cpp: In function ‘int cuv(trie*, int)’: user.cpp:73:1: warning: control reaches end of non-void function [-Wreturn-type] } ^