count-complete-tree-nodes.py

# Given a complete binary tree, count the number of nodes.

# Note:

# Definition of a complete binary tree from Wikipedia:
# In a complete binary tree every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.

# Example:

# Input: 
#     1
#    / \
#   2   3
#  / \  /
# 4  5 6

# Output: 6
# Definition for a binary tree node.
class TreeNode(object):
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None

class Solution(object):
    def countNodes(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        result=0
        temp=[]
        if not root:
            return result
        else:
            temp.append(root)
            while(len(temp)>0):
                node=temp.pop(0)
                result=result+1

                if node.left:
                    temp.append(node.left)
                if node.right:
                    temp.append(node.right)
            
            return result


            


# Sample code that creates a binary tree
def stringToTreeNode(input):
    input = input.strip()
    input = input[1:-1]
    if not input:
        return None

    inputValues = [s.strip() for s in input.split(',')]
    root = TreeNode(int(inputValues[0]))
    nodeQueue = [root]
    front = 0
    index = 1
    while index < len(inputValues):
        node = nodeQueue[front]
        front = front + 1

        item = inputValues[index]
        index = index + 1
        if item != "null":
            leftNumber = int(item)
            node.left = TreeNode(leftNumber)
            nodeQueue.append(node.left)

        if index >= len(inputValues):
            break

        item = inputValues[index]
        index = index + 1
        if item != "null":
            rightNumber = int(item)
            node.right = TreeNode(rightNumber)
            nodeQueue.append(node.right)
    return root

s=Solution()
tree=stringToTreeNode("[1,2,3,4,5,6,7,8]")
print(s.countNodes(tree))