Compilare: user.cpp: In function ‘void qsort(int, int)’: user.cpp:35:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(vec[ i ] < piv) i++; ^ user.cpp:37:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(vec[ j ] > piv) j--; ^ user.cpp: In function ‘int main()’: user.cpp:54:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0, elem; i < N; ++i) scanf("%d", &elem), vec.push( elem ); ^ user.cpp:50:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^ user.cpp:52:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&N); ^ user.cpp:54:74: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(int i = 0, elem; i < N; ++i) scanf("%d", &elem), vec.push( elem ); ^