invert a binary tree
//The Idea is to go through a post order traversal and swap the node at the end
//assume TreeNode is the tree structure
TreeNode* invertTree(TreeNode* root) {
if(root==NULL)
return root;
else
{
invertTree(root->left);
//assuming the fn did inverted everything till of left child
invertTree(root->right);
//assuming the fn inverted everything till of right child
//now swap the left child and right child nodes and return the node
TreeNode* temp=root->left;
root->left=root->right;
root->right=temp;
return(root);
//return the inverted node
}
}