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){
  while(u != NIL && k != u->key){
    if(k < u->key){
      u = u->left;
    }
    else u = u->right;
  }
  if(u == NIL) printf("no\n");
  else printf("yes\n");
  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 to be deleted
  Node x; // child of y

  if(z->left == NIL){
    Transplant(z,z->right);
  }
  else if(z->right == NIL){
    Transplant(z,z->left);
  }
  else{
    y = treeMinimum(z->right);
    if(y->parent != z){
      Transplant(y,y->right);
      y->right = z->right;
      y->right->parent =y;
    }
    Transplant(z,y);
    y->left = z->left;
    y->left->parent = y;
  }


}

void Transplant(Node u, Node v){
  if(u->parent == NIL){
    root = v;
  }
  else if(u == u->parent->left){
    u->parent->left = v;
  }
  else u->parent->right = v;
  if(v != NIL){
    v->parent = u->parent;
  }

}

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; // set parent
    if(z->key < x->key){
      x = x->left; // shift to left child
    }
    else{
      x = x->right; // shift to right child
    }
  }
  z->parent = y;

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

}

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

}
void preorder(Node u){
  if(u != NIL){
    printf(" %d",u->key);
    preorder(u->left);
    preorder(u->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] == 'f' ){
      scanf("%d", &x);
      treeSearch(root, k);
    } 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 'treeDelete':
main.c:54:5: error: implicit declaration of function 'Transplant' [-Wimplicit-function-declaration]
   54 |     Transplant(z,z->right);
      |     ^~~~~~~~~~
main.c: At top level:
main.c:74:6: warning: conflicting types for 'Transplant'; have 'void(struct node *, struct node *)'
   74 | void Transplant(Node u, Node v){
      |      ^~~~~~~~~~
main.c:54:5: note: previous implicit declaration of 'Transplant' with type 'void(struct node *, struct node *)'
   54 |     Transplant(z,z->right);
      |     ^~~~~~~~~~
main.c: In function 'main':
main.c:156:24: error: 'k' undeclared (first use in this function)
  156 |       treeSearch(root, k);
      |                        ^
main.c:156:24: note: each undeclared identifier is reported only once for each function it appears in