LeetCode 二叉樹，兩個子節點的最近的公共父節點

二叉樹

Lowest Common Ancestor of a Binary Tree

二叉樹的最近公共父親節點

https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree

https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {TreeNode} p
 * @param {TreeNode} q
 * @return {TreeNode}
 */
var lowestCommonAncestor = function(root, p, q) {
  let ancestor;
  // DFS 深度優先搜索
  const dfs = (root, p, q) => {
    if (root === null) {
      return false;
    }
    // 遞歸
    const leftSon = dfs(root.left, p, q);
    const rightSon = dfs(root.right, p, q);
    if ((leftSon && rightSon) || ((root.val === p.val || root.val === q.val) && (leftSon || rightSon))) {
      ancestor = root;
    }
    return leftSon || rightSon || (root.val === p.val || root.val === q.val);
  }
  dfs(root, p, q);
  return ancestor;
};

solutions

1. Recursive Approach

遞歸方法

2. Iterative using parent pointers

使用父指針進行迭代

3. Iterative without parent pointers

沒有父指針的迭代

refs

https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-tree/solution/

https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/solution/

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