Mirror image of a binary tree

Question

Suppose there is a tree:

             1
            / \\
           2   3
              / \\
             4   5

Then the mirror image will

Answer 1

Recursive Java Code

public class TreeMirrorImageCreator {

public static Node createMirrorImage(Node originalNode,Node mirroredNode){

    mirroredNode.setValue(originalNode.getValue());

    if(originalNode.getLeft() != null){
        mirroredNode.setLeft(createMirrorImage(originalNode.getRight(),new Node(0)));
    }

    if(originalNode.getRight() != null){
        mirroredNode.setRight(createMirrorImage(originalNode.getLeft(), new Node(0)));
    }

    return mirroredNode;

}
}

Answer 2

void mirror(struct node* node)  
{
   if (node==NULL)
   {
      return;
   }
   else 
   {
      struct node* temp;
      mirror(node->left);
      mirror(node->right);
      temp = node->left;
      node->left = node->right;
      node->right = temp;
    }
}

Answer 3

void mirror(node<t> *& root2,node<t> * root)
{
    if(root==NULL)
    {
        root2=NULL;
    }
    else {
        root2=new node<t>;
        root2->data=root->data;
        root2->left=NULL;
        root2->right=NULL;
        mirror(root2->left,root->right);
        mirror(root2->right,root->left);
    }
}

Answer 4

Sounds like homework.

It looks very easy. Write a recursive routine that depth-first visits every node and builds the mirror tree with left and right reversed.

struct node *mirror(struct node *here) {

  if (here == NULL)
     return NULL;
  else {

    struct node *newNode = malloc (sizeof(struct node));

    newNode->value = here->value;
    newNode->left = mirror(here->right);
    newNode->right = mirror(here->left);

    return newNode;
  }
}

This returns a new tree - some other answers do this in place. Depends on what your assignment asked you to do :)

Answer 5

Banal solution:

for each node in tree
    exchange leftchild with rightchild.

Answer 6

Recursive and Iterative methods in JAVA: 1) Recursive:

    public static TreeNode mirrorBinaryTree(TreeNode root){

    if(root == null || (root.left == null && root.right == null))
        return root;

    TreeNode temp = root.left;
    root.left = root.right;
    root.right = temp;

    mirrorBinaryTree(root.left);
    mirrorBinaryTree(root.right);


    return root;

}

2) Iterative:

public static TreeNode mirrorBinaryTreeIterative(TreeNode root){
    if(root == null || (root.left == null && root.right == null))
        return root;

    TreeNode parent = root;
    Stack<TreeNode> treeStack = new Stack<TreeNode>();
    treeStack.push(root);

    while(!treeStack.empty()){
        parent = treeStack.pop();

        TreeNode temp = parent.right;
        parent.right = parent.left;
        parent.left = temp;

        if(parent.right != null)
            treeStack.push(parent.right);
        if(parent.left != null)
            treeStack.push(parent.left);
    }
    return root;
}