Boundary_travsl_of_BT_gfg.cpp

/* A binary tree Node
struct Node
{
    int data;
    Node* left, * right;
}; */

class Solution
{
public:
     void traverseLeft(Node *root, vector<int> &ans)
     {
          if ((root == NULL) || (root->left == NULL && root->right == NULL))
               return;

          ans.push_back(root->data);

          if (root->left)
               traverseLeft(root->left, ans);
          else
               traverseLeft(root->right, ans);
     }

     void traverseLeaf(Node *root, vector<int> &ans)
     {
          if (root == NULL)
               return;

          if (root->left == NULL && root->right == NULL)
          {
               ans.push_back(root->data);
               return;
          }

          traverseLeaf(root->left, ans);
          traverseLeaf(root->right, ans);
     }

     void traverseRight(Node *root, vector<int> &ans)
     {
          if ((root == NULL) || (root->left == NULL && root->right == NULL))
               return;

          if (root->right)
               traverseRight(root->right, ans);
          else
               traverseRight(root->left, ans);

          ans.push_back(root->data);
     }

     vector<int> boundary(Node *root)
     {
          vector<int> ans;

          if (root->left == NULL && root->right == NULL)
          {
               ans.push_back(root->data);
               return ans;
          }

          ans.push_back(root->data);

          traverseLeft(root->left, ans);

          traverseLeaf(root->left, ans);
          traverseLeaf(root->right, ans);

          traverseRight(root->right, ans);

          return ans;
     }
};