Compilare: main.cpp: In function 'int main()': main.cpp:24:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][idx] == s[i-1][idx] && idx < s[i].size() && idx < s[i-1].size()) { ~~~~^~~~~~~~~~~~~ main.cpp:24:68: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i][idx] == s[i-1][idx] && idx < s[i].size() && idx < s[i-1].size()) { ~~~~^~~~~~~~~~~~~~~ main.cpp:14:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.in","r",stdin); ^ main.cpp:15:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.out","w",stdout); ^