Delete Node in a BST LeetCode solution in C++

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class Solution {
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 public:
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  TreeNode *deleteNode(TreeNode *root, int key) {
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    if (root)
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      if (key < root->val)
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        root->left = deleteNode(root->left, key); // We frecursively call the function
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                                                  // until we find the target node
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      else if (key > root->val)
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        root->right = deleteNode(root->right, key);
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      else {
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        if (!root->left && !root->right) return NULL; // No child condition
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        if (!root->left || !root->right)
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          return root->left ? root->left : root->right; // One child contion -> replace the node
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                                                        // with it's child Two child condition
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        TreeNode *temp = root->left;                    //(or) TreeNode *temp = root->right;
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        while (temp->right != NULL)
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          temp = temp->right;  //      while(temp->left != NULL) temp = temp->left;
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        root->val = temp->val; //       root->val = temp->val;
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        root->left = deleteNode(root->left,
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                                temp->val); //        root->right = deleteNode(root->right, temp);
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      }
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    return root;
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  }
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};