Compilare: user.cpp: In function ‘void build(int)’: user.cpp:19:8: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if ( index > 0 ) ^ user.cpp: In function ‘int main()’: user.cpp:50:37: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf ( f , "%d %d" , &n , &k ); ^