Language: C++

#include<stdio.h>
#include<stdlib.h>
#include<string>
#include<iostream>
using namespace std;

struct Node{
  int key;
  Node *right, *left, *parent;
}

Node *root, *NIL

Node * treeMinimum(Node *x0 {
  while( x->left != NIL ) x = x->left;
  return x;
}

Node * find(Node *u, int k) {
  while( u != NIL && k != u-key) {
    if ( k < u->key ) u = u->left;
    else u = u->right;
  }
  return u;
}

Node * treeSuccessor(Node *x){
  if ( x->right != NIL) return treeMinimum(x->right);
  Node *y = x->parent;
  while( y != NIL && x == y->right ) {
    x = y;
    y = y->parent;
  }
  return y;
}

void treeDelete(Node *z){
  Node *y;
  Node *x;

  if ( z->left == NIL || z->right == NIL ) y = z;
  else y = treeSuccessor(z);

  if ( y->left != NIL) {
    x = y->left;
  } else {
    x = y->right;
  }

  if ( x !== NIL ) {
    x->parent = y->parent;
  }

  if ( y->parent == NIL) {
    root = x;
  } else {
    if ( y == y->parent->left){
      y->parent->left = x;
    } else {
      y->parent->right = x;
    }
  }

  if ( y != z ) {
    z->key = y->key;
  }

  free(y);
}

void insert(int k) {
  Node *x, *y;
  x = root;
  y = NIL;

  Node *z;

  z = (Node *)malloc(sizeof(Node));
  z->key = k;
  z->right = NIL;
  z->left = NIL;

  while( x != NIL ) {
    y = x;
    if ( z->key < x->key) {
      x = x->left;
    } else {
      x = x->right;
    }
  }
  z->parent = y;

  if ( y == NIL ) z = root;
  else {
    if ( z->key < y->key ) {
      y->left = z;
    } else {
      y->right = z;
    }
  }   
}

void inorder(Node *u) {
  if( u == NIL) return
  inorder(u->left);
  print("%d", u->key);
  inorder(u->right);
}

void preorder(Node *u) {
  if( u == NIL) return;
  print("%d", u->key);
  preorder(u->left);
  preorder(u->right);
}

int main() {
  int n, i, x;
  string com;

  scanf("%d", &n);

  for ( i = 0; i < n; i++ ) {
    cin >> com;
    if ( com[0] == 'f') {
      scanf("%d", &x);
      Node *t = find(root, x);
      if ( t != NIL ) printf("yes\n");
      else printf("no\n");
    } else if ( com == "insert" ) {
      scanf("%d", &x);
      insert(x);
    } else if ( com == "print" ) {
      inorder(root);
      printf("\n");
      preorder(root);
      printf("\n");
    } else if ( com == "delete" ) {
      scanf("%d", &x);
      treeDelete(find(root, x));
    }
  }

  return 0;
}



Compiler output:
a.cc:12:6: error: expected initializer before '*' token
   12 | Node *root, *NIL
      |      ^
a.cc: In function 'Node* find(Node*, int)':
a.cc:20:15: error: 'NIL' was not declared in this scope
   20 |   while( u != NIL && k != u-key) {
      |               ^~~
a.cc:20:29: error: 'key' was not declared in this scope
   20 |   while( u != NIL && k != u-key) {
      |                             ^~~
a.cc: In function 'Node* treeSuccessor(Node*)':
a.cc:28:20: error: 'NIL' was not declared in this scope
   28 |   if ( x->right != NIL) return treeMinimum(x->right);
      |                    ^~~
a.cc:28:32: error: 'treeMinimum' was not declared in this scope
   28 |   if ( x->right != NIL) return treeMinimum(x->right);
      |                                ^~~~~~~~~~~
a.cc:30:15: error: 'NIL' was not declared in this scope
   30 |   while( y != NIL && x == y->right ) {
      |               ^~~
a.cc: In function 'void treeDelete(Node*)':
a.cc:41:19: error: 'NIL' was not declared in this scope
   41 |   if ( z->left == NIL || z->right == NIL ) y = z;
      |                   ^~~
a.cc:44:19: error: 'NIL' was not declared in this scope
   44 |   if ( y->left != NIL) {
      |                   ^~~
a.cc:50:12: error: expected primary-expression before '=' token
   50 |   if ( x !== NIL ) {
      |            ^
a.cc:50:14: error: 'NIL' was not declared in this scope
   50 |   if ( x !== NIL ) {
      |              ^~~
a.cc:54:21: error: 'NIL' was not declared in this scope
   54 |   if ( y->parent == NIL) {
      |                     ^~~
a.cc:55:5: error: 'root' was not declared in this scope
   55 |     root = x;
      |     ^~~~
a.cc: In function 'void insert(int)':
a.cc:73:7: error: 'root' was not declared in this scope
   73 |   x = root;
      |       ^~~~
a.cc:74:7: error: 'NIL' was not declared in this scope
   74 |   y = NIL;
      |       ^~~
a.cc: In function 'void inorder(Node*)':
a.cc:104:12: error: 'NIL' was not declared in this scope
  104 |   if( u == NIL) return
      |            ^~~
a.cc:106:3: error: 'print' was not declared in this scope; did you mean 'printf'?
  106 |   print("%d", u->key);
      |   ^~~~~
      |   printf
a.cc: In function 'void preorder(Node*)':
a.cc:111:12: error: 'NIL' was not declared in this scope
  111 |   if( u == NIL) return;
      |            ^~~
a.cc:112:3: error: 'print' was not declared in this scope; did you mean 'printf'?
  112 |   print("%d", u->key);
      |   ^~~~~
      |   printf
a.cc: In function 'int main()':
a.cc:127:22: error: 'root' was not declared in this scope
  127 |       Node *t = find(root, x);
      |                      ^~~~
a.cc:128:17: error: 'NIL' was not declared in this scope
  128 |       if ( t != NIL ) printf("yes\n");
      |                 ^~~
a.cc:134:15: error: 'root' was not declared in this scope
  134 |       inorder(root);
      |               ^~~~
a.cc:140:23: error: 'root' was not declared in this scope
  140 |       treeDelete(find(root, x));
      |                       ^~~~