Compilare: user.cpp: In function ‘void pre_line(int)’: user.cpp:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < aux.size(); i++) ^ user.cpp: In function ‘void pre_column(int)’: user.cpp:44:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i = 1; i < aux.size(); i++) ^ user.cpp: In function ‘void solve(int, int)’: user.cpp:49:9: warning: unused variable ‘i’ [-Wunused-variable] int i, xx, yy; ^ user.cpp:49:12: warning: unused variable ‘xx’ [-Wunused-variable] int i, xx, yy; ^ user.cpp:49:16: warning: unused variable ‘yy’ [-Wunused-variable] int i, xx, yy; ^ user.cpp: In function ‘int main()’: user.cpp:62:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("zoro.in","r",stdin); ^ user.cpp:63:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("zoro.out","w",stdout); ^ user.cpp:65:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ user.cpp:68:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &mat[i][j]); ^