A.1 B.1/2 C.2 D.4
A.2n-1 B.2n+2 C.2n+1 D.2n
A.葉結(jié)點(diǎn) B.空結(jié)點(diǎn) C.樹根結(jié)點(diǎn) D.分支結(jié)點(diǎn)