Compilare: user.cpp: In function ‘int main()’: user.cpp:9:36: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[strlen(s)-1]=s1[strlen(s1)-1]=NULL; ^ user.cpp:8:24: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s1,2000000,f); fgets(s,2000000,f);//puts(s1); ^ user.cpp:8:44: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(s1,2000000,f); fgets(s,2000000,f);//puts(s1); ^ user.cpp:20:5: warning: ‘n1’ may be used uninitialized in this function [-Wmaybe-uninitialized] for(i=1;i<=n1;i++) fprintf(g,"%d ",a[i]); ^