Compilare: user.cpp: In function ‘bool solve_color(int)’: user.cpp:79:9: warning: unused variable ‘i’ [-Wunused-variable] int i, j; ^ user.cpp:79:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j; ^ user.cpp: In function ‘int main()’: user.cpp:151:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < edges[i].size(); j++) ^ user.cpp:92:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("unlock.in","r",stdin); ^ user.cpp:93:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("unlock.out","w",stdout); ^ user.cpp:95:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for( scanf("%d", &t); t > 0; t--) { ^ user.cpp:98:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &n, &m, &k); ^ user.cpp:101:40: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &col[i][j]); ^