Compilare: user.cpp: In function ‘int main()’: user.cpp:24:20: warning: NULL used in arithmetic [-Wpointer-arith] while(op[i] != NULL) { ^ user.cpp:19:47: warning: unused variable ‘ant’ [-Wunused-variable] int res, ans, i, n, a, b, q, sz, nInsert, ant; ^ user.cpp:17:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("jstc.in", "r", stdin); ^ user.cpp:18:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("jstc.out", "w", stdout); ^ user.cpp:21:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n%s", &a, &b, op); ^