Compilare: main.cpp: In function 'double kruskals_algorithm(int)': main.cpp:72:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( i = 0 ; i < solution.size () && added_vertices < tree_size ; ++ i ) ~~^~~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:107:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( j = 0 ; j < v.size () ; ++ j ) ~~^~~~~~~~~~~ main.cpp:94:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ( "desen.in" , "r" , stdin ) ; ^ main.cpp:95:44: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ( "desen.out" , "w" , stdout ) ; ^ main.cpp:99:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d" , & n ) ; ^ main.cpp:103:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d%d" , & x , & y ) ; ^