Compilare: user.cpp: In function ‘int verif()’: user.cpp:23:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < S.size() - 1; i++) ^ user.cpp: In function ‘void backtracking()’: user.cpp:40:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(S.size() == N && verif()) ^ user.cpp: In function ‘void print()’: user.cpp:86:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(S.size() != N) ^ user.cpp:91:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < S.size(); i++) ^ user.cpp: In function ‘void read()’: user.cpp:59:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.in", "r", stdin); ^ user.cpp:60:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:63:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^ user.cpp: In function ‘void print()’: user.cpp:85:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("domino.out", "w", stdout); ^