Compilare: main.cpp: In function 'void nxt()': main.cpp:24:12: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sol[n] = NULL; ^~~~ main.cpp: In function 'void prv()': main.cpp:38:14: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sol[n] = NULL; ^~~~ main.cpp:49:16: warning: converting to non-pointer type 'char' from NULL [-Wconversion-null] sol[n] = NULL; ^~~~ main.cpp: In function 'int main()': main.cpp:59:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("calc.in", "r", stdin); ^ main.cpp:60:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("calc.out", "w", stdout); ^ main.cpp:62:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &p); ^ main.cpp:63:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &n); ^ main.cpp:64:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf ("%s", s); ^