Compilare: user.cpp: In function ‘int main()’: user.cpp:40:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(k=0; k<rev_arcs[j].size(); ++k) ~^~~~~~~~~~~~~~~~~~~ user.cpp:44:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<rev_arcs[0].size(); ++i) ~^~~~~~~~~~~~~~~~~~~ user.cpp:9:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hamilton.in", "r", stdin); ^ user.cpp:10:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("hamilton.out", "w", stdout); ^ user.cpp:13:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:25:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^ user.cpp:26:33: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &arcs[x][y]); ^