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  1. Prepare
  2. Data Structures
  3. Trees
  4. Tree: Preorder Traversal
  5. Discussions

Tree: Preorder Traversal

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452 Discussions

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  • nikolay_vlad_va1
     + 0 comments

    In some languages like Kotlin it gives only a main fucntion which doesn't have a Node class. And there's no explanation how the single array, that the input is giving, is sorted... I spent hours trying to figure out what the tree from the input should look like and I was trying to write a function to create the tree with Node class... So then I switched to Java and saw that the node object is given...

  • C191040_Alpha
     + 0 comments

    void solve(Node* root) { if(root == NULL) { return; } cout<data<<" "; solve(root->left); solve(root->right); }

    solve(root);

  • jaymikuvolcano
     + 0 comments

    Why it was showing main method in this?

  • mdsanz
     + 0 comments

    My Java 8 solutions

    Recursive approach

    public static void preOrder(Node root) {
    if (root == null) return;

    System.out.print(root.data + " ");
    preOrder(root.left);
    preOrder(root.right);
}

    Iterative approach

    public static void preOrder(Node root) {
    if (root == null) return;

    Stack<Node> stack = new Stack<>();
    stack.push(root);

    while (!stack.isEmpty()) {
        Node current = stack.pop();
        System.out.print(current.data + " ");
				
        if (current.right != null) {
            stack.push(current.right);
        }

        if (current.left != null) {
            stack.push(current.left);
        }
    }
}

  • emhhacker
     + 0 comments

    My Java solution with linear time complexity and constant space complexity:

    public static void preOrder(Node root) {
        if(root == null) return; //no val to be printed
        
        //print val
        System.out.print(root.data + " ");
        
        //recursively traverse thru left nodes first, the through right nodes
        preOrder(root.left);
        preOrder(root.right);
    }