Compilare: user.cpp: In function ‘void solve()’: user.cpp:53:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < children[i][c].size(); j++) ^ user.cpp:54:46: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = j + 1; k < children[i][c].size(); k++) { ^ user.cpp: In function ‘int main()’: user.cpp:79:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arbpal.in", "r", stdin); ^ user.cpp:80:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arbpal.out", "w", stdout); ^ user.cpp:82:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:85:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d ", &a, &b); ^ user.cpp:92:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%c ", &letter[i]); ^