#####   ######  #####    ###    #   #  ###  #   #  ######
##  ##  ##      ##  ##  ## ##   #   #   #   #   #  ##
#####   ####    #####   #   #   #   #   #   #   #  ####
##  #   ##      ##      ## ##    # #    #    # #   ##
##   #  ######  ##       ###      #    ###    #    ######

$ curl repovive.com/roadmaps/meta-interview-prep-v2/coding-patterns-ii-trees-graphs-advanced/leetcode-236-lowest-common-ancestor-of-a-binary-tree-implementation

░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████

#####   ######  #####    ###    #   #  ###  #   #  ######
##  ##  ##      ##  ##  ## ##   #   #   #   #   #  ##
#####   ####    #####   #   #   #   #   #   #   #  ####
##  #   ##      ##      ## ##    # #    #    # #   ##
##   #  ######  ##       ###      #    ###    #    ######

$ curl repovive.com/roadmaps/meta-interview-prep-v2/coding-patterns-ii-trees-graphs-advanced/leetcode-236-lowest-common-ancestor-of-a-binary-tree-implementation

Repovive

LeetCode 236 Lowest Common Ancestor of a Binary Tree - Implementation - Coding Patterns II: Trees, Graphs & Advanced | Meta Interview Prep | Repovive

Repovive.

Meta Interview Prep6 sections · 147 units8h total

Open in Course

LeetCode 236 Lowest Common Ancestor of a Binary Tree - Implementation

The approach

function lowestCommonAncestor(root, p, q):
    if root is None:
        return None
    if root == p or root == q:
        return root
    left = lowestCommonAncestor(root.left, p, q)
    right = lowestCommonAncestor(root.right, p, q)
    if left and right:
        return root
    return left if left else right

$O(n)$ time in the worst case (skewed tree visits every node). $O(h)$ space for the recursion stack, where $h$ is the tree height.