叶子结点的度为0,设叶子借你点为n0,度为1的结点的个数为n1,度为2的结点个数为n2,根据n0+n1+n2=n1+2*n2+1；可以算出,n0=n2+1；n2=n0-1=29；总结点数n=n0+n1+n2=30+40+29=99