检查树是否为二进制

Question

给出一个（n-ary）树。如何检查它是否是二进制文件？

Answer 1

  

如何检查它是否为二进制？

检查每个节点最多是否有2个孩子。

一些未经测试的（！）伪代码：

struct NTree {

  root: Node

  boolean isBinary() {
    return isBinary(root)
  }

  private boolean isBinary(Node n) {
    if (n has no child)
      return true
    elif (n has 1 child)
      return isBinary(n.children[0])
    elif (n has 2 children)
      return isBinary(n.children[0]) && isBinary(n.children[1])
    else
      return false
  }

  struct Node {
    children: List
  }
}

Answer 2

使用任何tree traversal algorithm访问每个节点，如果任何节点在途中有两个以上的子节点，则返回false。

Answer 3

遍历它并检查子节点数≤2

Answer 4

为避免使用递归，可以使用广度优先遍历。

Queue q <- empty
Enqueue(q, root)
while (q is not empty)
    do u <- Dequeue(q)
       for all u's children
           if they are more than 2, then quit, this is not a binary tree
           else Enqueue(q, all children one by one)
Since we didn't quit in the loop, this is a binary tree