Leetcode 236. Lowest Common Ancestor of a Binary Tree

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本文介绍了一种寻找二叉树中两个节点的最低公共祖先(LCA)的有效递归算法。通过递归地搜索左子树和右子树来定位目标节点，如果在左右子树中都能找到目标节点，则当前根节点即为最低公共祖先。

public class Solution {
    // Recursively call lowestCommonAncestor to find node p and q,
    // If found return, else return null
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root == null)
            return root;
        if (root == p || root == q)     // found a node, return itself
            return root;
        TreeNode left = lowestCommonAncestor(root.left, p, q);       // find p and q in the left tree
        TreeNode right = lowestCommonAncestor(root.right, p, q);     // find p and q in the right tree
        if (left != null && right != null)              // both p and q can be found in the left and right tree, then root is the LCA
            return root;
        return left != null ? left : right;     // return non-null node in left and right or null if both left and right are null
    }
}