Compilare: user.cpp: In function ‘void radix_sort(int)’: user.cpp:19:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<cifre[j].size();++k)x[++n] = cifre[j][k]; ^ user.cpp: In function ‘int main()’: user.cpp:27:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("radixsort.in","r",stdin); ^ user.cpp:28:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("radixsort.out","w",stdout); ^ user.cpp:29:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d",&n,&a,&b,&c); ^