Compilare: user.cpp: In function ‘int main()’: user.cpp:15:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<strlen(s))if(s[i]==' ')strcpy(s+i,s+i+1);else i++; ^ user.cpp:17:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<strlen(s)) ^ user.cpp:23:51: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(s[i]>='0'&&s[i]<='9'&&i<strlen(s)) ^