Compilare: user.cpp: In function ‘void build(int, int, int)’: user.cpp:24:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<a[s].size()&&j<a[d].size()) ^ user.cpp:24:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<a[s].size()&&j<a[d].size()) ^ user.cpp:37:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(;i<a[s].size();i++) ^ user.cpp:40:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(;j<a[d].size();j++) ^