Compilare: main.cpp: In function 'int h(std::__cxx11::string)': main.cpp:20:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0 ; i < s.length() ; i ++) ~~^~~~~~~~~~~~ main.cpp: In function 'int dup()': main.cpp:35:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0 ; j < G[i].size() ; j ++) ~~^~~~~~~~~~~~~ main.cpp:39:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k = j + 1 ; k < G[i].size() ; k ++) ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:63:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("strdup.in" , "r" , stdin); ^ main.cpp:64:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("strdup.out" , "w" , stdout); ^ main.cpp:66:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n" , &t); ^