Que235.java

/**
 * @author: hyl
 * @date: 2019/08/03
 **/
public class Que235 {

    class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) { val = x; }
    }

    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {

        if (root.val > p.val && root.val > q.val){
            return lowestCommonAncestor(root.left,p,q);
        }
        if (root.val < p.val && root.val < q.val){
            return lowestCommonAncestor(root.right,p,q);
        }

        return root;
    }

    public TreeNode lowestCommonAncestor1(TreeNode root, TreeNode p, TreeNode q) {

        while (root != null) {
            if (root.val > p.val && root.val > q.val) {
                root = root.left;
            } else if (root.val < p.val && root.val < q.val) {
                root = root.right;
            } else {
                return root;
            }
        }
        return root;
    }
}