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import java.lang.*;
import java.util.*;
import node.*;
class ValidateTree {
public static boolean isValidBST(TreeNode root) {
if (root.left == null || root.right == null)
return true;
else if (root.left.val > root.val || root.right.val < root.val)
return false;
boolean l = isValidBST(root.left);
boolean r = isValidBST(root.right);
return l && r ? true : false;
}
public static void main(String[] args) {
TreeNode leftLeaf = new TreeNode(1);
TreeNode middleLeaf = new TreeNode(3);
TreeNode rightLeaf = new TreeNode(6);
TreeNode rightParent = new TreeNode(4);
TreeNode root = new TreeNode(5, leftLeaf, rightParent);
System.out.println(isValidBST(root));
}
}
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