LeetCode236找二叉树最近公共祖先，不知道哪里出问题了，思路应该是对的吧

来源：7-7 二分搜索树中的问题 Lowest Common Ancestor of a Binary Search Tree

不考过程序员不改名字

2022-03-22

    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
        if (root==null||p==null||q==null){
            return null;
        }
        //p在左子树
        boolean pInLeft = existNode(root.left,p.val);
        //q在左子树
        boolean qInLeft = existNode(root.left,q.val);
        //p在右子树
        boolean pInRight = !pInLeft;
        //q在右子树
        boolean qInRight = !qInLeft;
        if (pInLeft&&qInLeft){
            return lowestCommonAncestor(root.left,p,q);
        }else if (pInRight&&qInRight){
            return lowestCommonAncestor(root.right,p,q);
        }else {
            return root;
        }
    }
    public boolean existNode(TreeNode root,int target){
        if (root==null){
            return false;
        }
        if (root.val == target){
            return true;
        }
        return existNode(root.left,target)||existNode(root.right,target);
    }