[刷题]Lowest Common Ancestor

最新推荐文章于 2025-02-03 15:37:10 发布

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本文介绍了一种寻找二叉搜索树中两个节点的最低公共祖先(LCA)的方法。通过递归深度优先搜索(DFS)，该算法有效地解决了这一问题，并提供了完整的Java实现代码。

[LintCode]Lowest Common Ancestor

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: The root of the binary search tree.
     * @param A and B: two nodes in a Binary.
     * @return: Return the least common ancestor(LCA) of the two nodes.
     */
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode A, TreeNode B) {
        // 2015-3-23 DFS
        if (A == null || B ==null) {
            return null;
        }
        if (root == null || root == A || root == B) {
            return root;
        }
        
        // divide
        TreeNode left = lowestCommonAncestor(root.left, A, B);
        TreeNode right = lowestCommonAncestor(root.right, A, B);
        
        // conquer
        if (left != null && right != null) {
            return root;
        } else if (left != null) {
            return left;
        } else if (right != null) {
            return right;
        } else {
            return null;
        }
    }
}