/**

• 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 {

  pair< TreeNode * , TreeNode * > Gettarget( TreeNode * & root , int & key )
  {
  TreeNode * prev = nullptr ;
  TreeNode * curr = root ;

     while ( curr != nullptr )
     { 
       prev = curr ; 
  
       if( key == curr->val )
          break ;
       else if ( key > curr->val )
          curr = curr->right ;    
       else
          curr = curr->left ;
     }
  
     return { prev , curr }  ; 
  

  }

  void insert( TreeNode * root , TreeNode * insertedNode )
  {
  TreeNode * prev = nullptr , * curr = root ;

    bool isRight = false ;
  
    while ( curr != nullptr  )
    {
       prev = curr  ;
  
       if( insertedNode->val > curr->val )
       {
            isRight = 1 ;
            curr = curr->right  ;
       }
       else
       {
            isRight = 0 ;
            curr = curr->left ;
       }
  
    }
  
    if( isRight )
    {
       prev->right = insertedNode ;
    }
    else
    {
       prev->left = insertedNode ;
    }
  

  }
  public:
  TreeNode* deleteNode(TreeNode* root, int key)
  {

    pair< TreeNode * , TreeNode * >  P =   Gettarget( root , key )  ;
  
    if( P.second == nullptr ) //key is not found , nothing to delete 
       return root ;
  
    // else
  
    TreeNode * prev = P.first , * curr = P.second  ; 
  
    if( curr->left == nullptr  && curr->right  == nullptr )    // zero  child 
    {
        if( prev == nullptr )     // delete the root node 
        { 
            delete curr ;
            root = nullptr ;
            return root ;
  
        }
        else
        {                 
  
           if(  prev->left == curr )
                prev->left = nullptr ;
           else
                prev->right = nullptr ;
  
           delete curr ;
           curr = nullptr ;
           return root ;          
  
        }
    }  
  
    else if (  curr->left  != nullptr  && curr->right  == nullptr )   // single child 
    {
       if( prev == nullptr )
       { 
           TreeNode * ans = curr->left ;
           curr->left = nullptr ;
           delete curr ;
           curr = nullptr ;
           return ans ;
  
       }   
       else
       {
           TreeNode * ans = curr->left ;
           curr->left = nullptr ;
  
           if(  prev->left == curr )
              prev->left = ans ; 
           else
              prev->right = ans ;
  
            delete curr ;
           curr = nullptr ;
            return root ;
  
       }
    }
    else if (  curr->left  == nullptr  && curr->right  != nullptr )
    {
       if( prev == nullptr )
       { 
           TreeNode * ans = curr->right ; 
           curr->left = nullptr ;
           delete curr ;
           curr = nullptr ;
           return ans ;
  
       }
       else
       {
           TreeNode * ans = curr->right ; 
           curr->right = nullptr ;
  
           if(  prev->left == curr )
              prev->left = ans ; 
           else
              prev->right = ans ;
  
            delete curr ; 
           curr = nullptr ;
            return root ;
  
       }
  
    }
  
    else 
    {
  
       if( prev == nullptr )
       {
           TreeNode * left = curr->left , * right = curr->right ;
           insert( right , left )  ;
           curr->left = curr->right = nullptr ;
           delete curr ;
           curr = nullptr ;
  
           return right ; 
  
       }
       else
       { 
  
           TreeNode * left = curr->left , * right = curr->right ;
           insert( right , left )  ;
           curr ->left  = curr->right = nullptr ;
           if( prev->left == curr )
              prev->left = right ;
           else
              prev->right = right ;   
           delete curr ; 
           curr = nullptr ;
  
           return root ;
  
       }
  
  
    }
  

  }
  };

i was trying to know why the error is occuring ? i dont want the soln , i already knows that , you can respone the correct eddited part of the code , thanks
.