Error in binary tree

I do not know what I am missing in my code that causes this following error:

Code:

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Error E2285 TreeProgram.cpp 40: Could not find a match for 'Tree::Tree(string)' in function Tree::InsertTree(Tree * &,string)

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This is my code.

Code:

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#include <iostream>
#include <string>
using namespace std;

class Tree
{
        public:
                  int item;
                Tree* root;       
                Tree* left;
                Tree* right;

       
        int countTree( Tree* root );
        void InsertTree(Tree *&root, string newItem );         
};

Tree::Tree(){
        root = new Tree;
       
        root->item = 0;
        root->left = NULL;
        root->right = NULL;
}
               
int Tree::countTree( Tree* root ) {

    if ( root == NULL )
          return 0; 
        else {
          int count = 1; 
          count += countTree(root->left);                                             
          count += countTree(root->right);                                     
                          return count; 
        }
} 


void Tree::InsertTree(Tree *&root, string newItem) {

  if ( root == NULL ){
          root = new Tree( newItem ); // <<<<<<<<<<<HERE IS THE PROBLEM <<<
            return;
 }
  else if ( newItem < root->item ) {
      InsertTree( root->left, newItem );
  }
  else {
      InsertTree( root->right, newItem );
  }
}
 
int main ()
{
        Tree* root;       
        int loop=0;
          int num;
          while(loop == 0){
                  cout << " Select an Option:" << endl; 
                  cout << "(1) Enter a new calculation string." << endl; 
                  cout << "(2) Print the current tree in infix notation." << endl; 
                  cout << "(3) Print the current tree in prefix notation." << endl; 
                  cout << "(4) Print the current tree in postfix notation." << endl; 
                  cout << "(5) Calculate the result of the current tree." << endl; 
                  cout << "(6) Exit the program." << endl; 
                  cout << " " << endl; 
                  cin >> num;
               
               
                if ( num ==6){
                        break;
                }
  }
  return 0;
}

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You haven't defined a Tree constructor that takes a string parameter, the line of code in questions is passing a string!

I have updated the code above and added the constructor to it, so I got these following errors that don't make sense to me:

Code:

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Error E2171 TreeProgram.cpp 20: Body has already been defined for function 'Tree::Tree()'
Error E2015 TreeProgram.cpp 23: Ambiguity between 'std::basic_string<char,std::char_traits<char>,std::allocator<char> >::operator =(const char *)' and 'std::basic_string<char,std::char_traits<char>,std::allocator<char> >::operator =(char)' in function Tree::Tree()
Error E2285 TreeProgram.cpp 44: Could not find a match for 'Tree::Tree(string)' in function Tree::InsertTree(Tree * &,string)

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How did you actually update the code? Do you now have a constructor with a signature like Tree::Tree(string Item) ?