帶權路徑長度

int CalcWPL(BiTree T,int d){
	static int wpl;
	if(!(T->lchild)&&!(T->rchild)){
		wpl+=(T->weight)*d;
	}
	if(T->lchild)CalcWPL(T->lchild,d+1);
	if(T->rchild)CalcWPL(T->rchild,d+1);
	return wpl;
}//調用時傳入0給d