155. Minimum Depth of Binary Tree

最新推荐文章于 2023-12-15 03:22:29 发布

zoojing

最新推荐文章于 2023-12-15 03:22:29 发布

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分类专栏： python lintcode 文章标签： python lintcode

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本文介绍了一种求解二叉树最小深度的有效算法。通过递归或非递归方式，该算法能找出从根节点到最近叶子节点的最短路径上的节点数。文中提供了Python实现代码，并详细解释了每一步的逻辑。

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Given a binary tree, find its minimum depth.

The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.

Example
Given a binary tree as follow:

The minimum depth is 2.

Python:

    """
Definition of TreeNode:
class TreeNode:
def __init__(self, val):
    self.val = val
    self.left, self.right = None, None
"""
class Solution:
"""
@param root: The root of binary tree.
@return: An integer
""" 
'''
# non recursion
def minDepth(self, root):
    if root is None:
        return 0
    depth = 0
    stack = [root]
    while stack:
        next = []
        depth += 1
        for item in stack:
            if item.left is None and item.right is None:
                return depth
            if item.left:
                next.append(item.left)
            if item.right:
                next.append(item.right)
        stack = next
    return depth
'''

'''
def minDepth(self, root):
    if root is None:
        return 0
    if root.left is None and root.right is None:
        return 1
    elif root.left and not root.right:
        return self.minDepth(root.left) + 1
    elif root.right and not root.left:
        return self.minDepth(root.right) + 1
    else:
        return min(self.minDepth(root.left), self.minDepth(root.right)) + 1
'''

def minDepth(self, root):
    if root is None:
        return 0
    left = self.minDepth(root.left)
    right = self.minDepth(root.right)
    if left == 0 or right == 0:
        return left + right + 1
    else:
        return min(left, right) + 1