Mirror of a Binary Tree

Question: Mirror of a Binary Tree T is another Binary Tree M(T) with left and right children of all non-leaf nodes interchanged.

Algorithm - Mirror(tree):

(1)  Call Mirror for left-subtree    i.e., Mirror(left-subtree)
(2)  Call Mirror for right-subtree  i.e., Mirror(left-subtree)
(3)  Swap left and right subtrees.
          temp = left-subtree
          left-subtree = right-subtree
          right-subtree = temp

Solution:

void mirror(TreeNode T)

{

  If(T != null) {   

    

    // do the subtrees recursively

    mirror(T.left);

    mirror(T.right);

    // swap the pointers in this node 

    TreeNode temp = T.left;

    T.left = T.right;

    T.right = temp;

  }

}