Compilare: user.cpp: In function ‘int main()’: user.cpp:20:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(bc);i++) ~^~~~~~~~~~~ user.cpp:50:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<strlen(bc);i++) ~^~~~~~~~~~~ user.cpp:70:35: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(i-1>=0) ^