BstLowestCommonAncestor

  • 2022-12-14
  • 浏览 (541)

BstLowestCommonAncestor.java 源码

package algorithm.recursion;

/**
 * @author roseduan
 * @time 2020/9/24 9:11 下午
 * @description 二叉搜索树的最近公共祖先
 */
public class BstLowestCommonAncestor {

    /**
     * 递归的方式
     */
    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (p.val > root.val && q.val > root.val) {
            return lowestCommonAncestor(root.right, p, q);
        }
        if (p.val < root.val && q.val < root.val){
            return lowestCommonAncestor(root.left, p, q);
        }
        return root;
    }

    /**
     * 递归改成循环
     */
    public TreeNode lowestCommonAncestor2(TreeNode root, TreeNode p, TreeNode q) {
        while (root != null) {
            if (p.val > root.val && q.val > root.val) {
                root = root.right;
            } else if (p.val < root.val && q.val < root.val) {
                root = root.left;
            } else {
                return root;
            }
        }
        return null;
    }

    public class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int val) { this.val = val; }
        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }
}

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