Invert a Binary Tree.cpp

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */


class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
      if(root==nullptr || (root->left ==  nullptr && root->right == nullptr)) return root;
      else if(root->left != nullptr && root->right == nullptr)
      {
        root->right = root->left;
        root->left = nullptr;
        invertTree(root->right);
      }
      else if(root->left == nullptr && root->right != nullptr)
      {
        root->left = root->right;
        root->right = nullptr;
        invertTree(root->left);
      }
      else
      {
        TreeNode* temp;
        temp = root->left;
        root->left = root->right;
        root->right = temp;
        invertTree(root->left);
        invertTree(root->right);
      }
      return root;        
    }
};