Compilare: main.cpp: In function 'int main()': main.cpp:21:47: 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:21:68: 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:11:36: 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:12:38: 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); ^ main.cpp:13:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] int n;scanf("%d",&n); ^