Language: C

#include<stdio.h>
#include<stdlib.h>



struct node{
  struct node *right;
  struct node *left;
  struct node *parent;
  int key;
};
typedef struct node * Node;
#define NIL NULL

Node root;

Node treeMinimum(Node x){
  while(x.left!=NIL){
    x=x.left;
  }
  return x;

}

Node treeSearch(Node u, int k){
  if(u==NIL || k==u.key)return u;
  if(k<u.key)return treeSearch(u.left,k);
  else return treeSearch(u.right,k);

}

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

void treeDelete(Node z){
  Node y; // node to be deleted
  Node x; // child of y
  /* 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;*/
}

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

  z = malloc(sizeof(struct node));
  z->key = k;
  z->left = NIL;
  z->right = NIL;

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

void inorder(Node u){
  if(u->left!=NIL) inorder(u->left);
  printf("%d",u->key);
  if(u->right!=NIL)  inorder(x->right);
  

}
void preorder(Node u){
printf("%d",u->key);
if(u->left!=NIL) preorder(u->left);
if(u->right!=NIL)  preorder(x->right);
}


int main(){
  int n, i, x;
  char com[20];
  scanf("%d", &n);

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

  return 0;
}

Compiler output:
main.c: In function 'treeMinimum':
main.c:18:10: error: 'x' is a pointer; did you mean to use '->'?
   18 |   while(x.left!=NIL){
      |          ^
      |          ->
main.c:19:8: error: 'x' is a pointer; did you mean to use '->'?
   19 |     x=x.left;
      |        ^
      |        ->
main.c: In function 'treeSearch':
main.c:26:20: error: 'u' is a pointer; did you mean to use '->'?
   26 |   if(u==NIL || k==u.key)return u;
      |                    ^
      |                    ->
main.c:27:9: error: 'u' is a pointer; did you mean to use '->'?
   27 |   if(k<u.key)return treeSearch(u.left,k);
      |         ^
      |         ->
main.c:27:33: error: 'u' is a pointer; did you mean to use '->'?
   27 |   if(k<u.key)return treeSearch(u.left,k);
      |                                 ^
      |                                 ->
main.c:28:27: error: 'u' is a pointer; did you mean to use '->'?
   28 |   else return treeSearch(u.right,k);
      |                           ^
      |                           ->
main.c: In function 'treeSuccessor':
main.c:34:7: error: 'x' is a pointer; did you mean to use '->'?
   34 |   if(x.right!=NIL) return treeMinimum(x.right);
      |       ^
      |       ->
main.c:34:40: error: 'x' is a pointer; did you mean to use '->'?
   34 |   if(x.right!=NIL) return treeMinimum(x.right);
      |                                        ^
      |                                        ->
main.c:35:6: error: 'x' is a pointer; did you mean to use '->'?
   35 |   y=x.parent;
      |      ^
      |      ->
main.c:36:23: error: 'y' is a pointer; did you mean to use '->'?
   36 |   while(y!=NIL && x==y.right){
      |                       ^
      |                       ->
main.c:38:8: error: 'y' is a pointer; did you mean to use '->'?
   38 |     y=y.parent;
      |        ^
      |        ->
main.c: In function 'insert':
main.c:97:12: error: 'Z' undeclared (first use in this function)
   97 |   else if (Z->key < y->key){
      |            ^
main.c:97:12: note: each undeclared identifier is reported only once for each function it appears in
main.c: In function 'inorder':
main.c:110:30: error: 'x' undeclared (first use in this function)
  110 |   if(u->right!=NIL)  inorder(x->right);
      |                              ^
main.c: In function 'preorder':
main.c:117:29: error: 'x' undeclared (first use in this function)
  117 | if(u->right!=NIL)  preorder(x->right);
      |                             ^