Compilare: user.cpp: In function ‘void build()’: user.cpp:55:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A[x].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:92:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gather.in", "r", stdin); ^ user.cpp:93:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("gather.out", "w", stdout); ^ user.cpp:95:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &k, &n, &m); ^ user.cpp:100:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &nodes[i]); ^ user.cpp:105:45: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &a, &b, &c, &d); ^