Compilare: user.cpp: In function ‘unsigned int b2d(std::string)’: user.cpp:10:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<x.size();++i) ^ user.cpp:11:42: warning: suggest parentheses around ‘-’ inside ‘<<’ [-Wparentheses] ans += x[i]=='1'? 1 << x.size()-i-1 : 0; ^