check_equal_tree.cpp

#include <iostream>

class Tree {
private:
  struct TreeNode {
    int val;
    TreeNode *l, *r;
    TreeNode(int val, TreeNode *l = nullptr, TreeNode *r = nullptr) :
      val(val), l(l), r(r) {}
  };
  size_t size;
  TreeNode *root;
  TreeNode *__insert(TreeNode *root, TreeNode *node) {
    if(!root)
      return node;
    if(node->val < root->val)
      root->l = __insert(root->l, node);
    else
      root->r = __insert(root->r, node);
    return root;
  }
  bool __all_nodes_equal(TreeNode *root, int key) {
    if(!root) return true;
    if(root->val != key)
      return false;
    else
      return __all_nodes_equal(root->l, key) && __all_nodes_equal(root->r, key);
  }
public:
  Tree() : size(0), root(nullptr) {}
  void insert(int val) {
    root = __insert(root, new TreeNode(val));
  }
  bool all_nodes_equal() {
    return __all_nodes_equal(root, root->val);
  }
};

int main() {
  Tree t;
  int val;
  while(std::cin >> val) {
    t.insert(val);
  }
  std::cout << t.all_nodes_equal();
}