Language: C

#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->right!=NIL){
    x=x->right;
  }
  return x;
}

Node treeMaximum(Node x){
  while(x->right!=NIL){
    x=x->right;
  }
  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;

  //code
  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;
  }
}

void inorder(Node u){

  if(u==NIL){
    return;
  }
  inorder(u->left);
  printf(" %d",u->key);
  inorder(u->right);
  }
}
void preorder(Node u){
  
  if(u==NIL){
    return;
  }
  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] == '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 'inorder':
main.c:127:3: error: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
  127 |   printf(" %d",u->key);
      |   ^~~~~~
main.c:2:1: note: include '<stdio.h>' or provide a declaration of 'printf'
    1 | #include<stdlib.h>
  +++ |+#include <stdio.h>
    2 | 
main.c:127:3: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
  127 |   printf(" %d",u->key);
      |   ^~~~~~
main.c:127:3: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c: At top level:
main.c:130:1: error: expected identifier or '(' before '}' token
  130 | }
      | ^
main.c: In function 'preorder':
main.c:136:3: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
  136 |   printf(" %d",u->key);
      |   ^~~~~~
main.c:136:3: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c: In function 'main':
main.c:145:3: error: implicit declaration of function 'scanf' [-Wimplicit-function-declaration]
  145 |   scanf("%d", &n);
      |   ^~~~~
main.c:145:3: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:145:3: warning: incompatible implicit declaration of built-in function 'scanf' [-Wbuiltin-declaration-mismatch]
main.c:145:3: note: include '<stdio.h>' or provide a declaration of 'scanf'
main.c:152:23: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
  152 |       if ( t != NIL ) printf("yes\n");
      |                       ^~~~~~
main.c:152:23: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:153:12: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
  153 |       else printf("no\n");
      |            ^~~~~~
main.c:153:12: note: include '<stdio.h>' or provide a declaration of 'printf'
main.c:159:7: warning: incompatible implicit declaration of built-in function 'printf' [-Wbuiltin-declaration-mismatch]
  159 |       printf("\n");
      |       ^~~~~~
main.c:159:7: note: include '<stdio.h>' or provide a declaration of 'printf'