111.-minimum-depth-of-binary-tree.md

111. Minimum Depth of Binary Tree

{% tabs %} {% tab title="Python" %}

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

class Solution:
    def minDepth(self, root: TreeNode) -> int:
        if not root: return 0
        ans = 1
        q = collections.deque()
        q.append(root)
        while q:
            len_q = len(q)
            for i in range(len_q):
                node = q.popleft()
                if node.left:
                    q.append(node.left)
                if node.right:
                    q.append(node.right)
                elif not node.left and not node.right :
                    return ans
                
            ans += 1
            
            

            

{% endtab %}

{% tab title="recursive" %}

 class Solution:
    def minDepth(self, root: TreeNode) -> int:
        if not root: return 0

        left = self.minDepth(root.left) 
        right = self.minDepth(root.right)
        if left == 0 or right == 0: # 并不是都没有儿子
            return left + right + 1
        return min(left, right) + 1

{% endtab %} {% endtabs %}