Compilare: user.cpp: In function ‘void CountingSort(int*, int*, int)’: user.cpp:11:60: warning: operation on ‘i’ may be undefined [-Wsequence-point] for(; i != 255; index[++i] = index[~-i] + frequence[~-i]); ^ user.cpp:11:60: warning: operation on ‘i’ may be undefined [-Wsequence-point] user.cpp: In function ‘int main()’: user.cpp:18:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("algsort.in", "r", stdin); ^ user.cpp:19:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("algsort.out", "w", stdout); ^ user.cpp:21:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:25:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &v[i]); ^