Compilare: main.cpp: In function 'void build_kdtree(kdtree_node*, int, std::vector<std::pair<int, int> >*)': main.cpp:53:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = mid; i < points->size(); i++) ~~^~~~~~~~~~~~~~~~ main.cpp: In function 'void read_input()': main.cpp:26:33: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("snpid.in", "r", stdin); ^ main.cpp:27:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ main.cpp:30:21: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &y[i]); ^ main.cpp: In function 'void write_output()': main.cpp:125:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("snpid.out", "w", stdout); ^