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  1. Prepare
  2. Data Structures
  3. Trees
  4. Is This a Binary Search Tree?
  5. Discussions

Is This a Binary Search Tree?

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903 Discussions

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  • mazharnaqvi786
     + 0 comments

    None of the languages I use are setup properly to work when running code?

  • mdsanz
     + 0 comments

    My Java 8 Solution

    boolean checkBST(Node root) {
        return isBST(root, null, null);
    }

    boolean isBST(Node root, Integer min, Integer max) {
        if (root == null) {
            return true;
        }
        
        if ((min != null && root.data <= min) || (max != null && root.data >= max)) {
            return false;
        }
        
        return isBST(root.left, min, root.data) && isBST(root.right, root.data, max);
    }

  • aryankatiyarKN33
     + 0 comments
    1. traverse the array in tree.
    2. apply the recursive approach

  • manceraaxel
     + 0 comments
    """ Node is defined as
class node:
  def __init__(self, data):
      self.data = data
      self.left = None
      self.right = None
"""

# Could've used inorder traversal and, every time a node is added to results array, check if it's actually greater than the value prior to it, but decided to use try this approach instead, lol.

def check_binary_search_tree_(root):
    # node, min val in current range, max val in current range. Range updates every time a new node is visited. Given the range values, I can implicitly tell whether I'm moving either to the left or to the right.
    stack = [(root, 0, 10e4)]

    while stack:
        current, min_in_range, max_in_range = stack.pop()
        if not (min_in_range < current.data < max_in_range):
            return False

        if current.right:
            stack.append((current.right, current.data, max_in_range))
        if current.left:
            stack.append((current.left, min_in_range, current.data))

    return True

  • muhammadAqib12
     + 0 comments
    Initially, I was failing some test cases but then i changed the condition in inorder function to check for >= instead of > and then it worked. This means that if a node has a parent or a child equal to itself then it voilates the BST property. 

bool inorder(Node* root,vector<int>& vec){
    if(!root){
        return true;
    }
    bool l=inorder(root->left,vec);
    if(vec.size() && vec.back()>=root->data){
        return false;
    }
    vec.push_back(root->data);
    bool r=inorder(root->right,vec);

    return l && r;

}
bool checkBST(Node* root) {
    if(!root){
        return false;
    }
    vector<int> vec;
    if(inorder(root,vec)){
        return true;
    }

    return false;
}