Compilare: main.cpp: In function 'int main()': main.cpp:50:13: warning: unused variable 'val' [-Wunused-variable] int val = toposort[i]; ^~~ main.cpp:58:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < sol[i].size(); j++) { ~~^~~~~~~~~~~~~~~ main.cpp:32:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.in", "r", stdin); ^ main.cpp:33:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.out", "w", stdout); ^ main.cpp:34:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ main.cpp:37:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^