Problem p02285 (C++)

Buggy submission (status: Runtime Error):
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
using namespace std;
// NIL is NULL
#define NIL NULL
// Node structure
struct Node {
  int key;
  struct Node *parent;
  struct Node *leftc;
  struct Node *rightc;
};
// define Nodepointer
typedef struct Node *Nodepointer;

// root
Nodepointer root;

// function insert
void insert(int k) {
  Nodepointer x, y, z;
  y = NIL;
  x = root;
  // make memory
  z = new struct Node();

  z->key = k;
  z->leftc = NIL;
  z->rightc = NIL;

  while (x != NIL) {
    y = x;
    if (z->key < x->key)
      x = x->leftc;
    else
      x = x->rightc;
  }

  z->parent = y;

  if (y == NIL)
    root = z;

  else if (z->key < y->key)
    y->leftc = z;

  else
    y->rightc = z;
}

// function search
Nodepointer find(Nodepointer now, int data) {
  if (now == NIL || data == now->key)
    return now;
  if (data < now->key)
    return find(now->leftc, data);
  else
    return find(now->rightc, data);
}

// function treeminimum
Nodepointer treeminimum(Nodepointer x) {
  while (x->leftc != NIL) {
    x = x->leftc;
  }
  return x;
}
// function treesuccerssor
Nodepointer treesuccessor(Nodepointer x) {
  Nodepointer y;
  if (x->rightc != NIL)
    return treeminimum(x->rightc);
  y = x->parent;
  while (y != NIL && x == x->rightc) {
    x = y;
    y = y->parent;
  }
  return y;
}
// function treedelete
void treedelete(Nodepointer z) {
  Nodepointer x, y;
  if (z->leftc == NIL || z->rightc == NIL)
    y = z;
  else
    y = treesuccessor(z);

  if (y->leftc != NIL)
    x = y->leftc;
  else
    x = y->rightc;

  if (x != NIL)
    x->parent = y->parent;
  if (y->parent == NIL)
    root = x;
  else if (y == y->parent->leftc)
    y->parent->leftc = x;
  else
    y->parent->rightc = x;

  if (y != z)
    z->key = y->key;
  // free memory
  delete z;
}

// print
void inorderprint(Nodepointer now) {
  if (now != NIL) {
    inorderprint(now->leftc);
    printf(" %d", now->key);
    inorderprint(now->rightc);
  }
}

void preorderprint(Nodepointer now) {
  if (now != NIL) {
    printf(" %d", now->key);
    preorderprint(now->leftc);
    preorderprint(now->rightc);
  }
}

int main() {

  int n, i, j, data;
  Nodepointer del;
  char str[10];
  // load n
  scanf("%d", &n);
  // load commnad and key
  for (i = 0; i < n; i++) {
    scanf("%s", str);
    // insert
    if (strcmp(str, "insert") == 0) {
      scanf("%d", &data);
      insert(data);
    }
    // find
    else if (strcmp(str, "find") == 0) {
      scanf("%d", &data);
      if (find(root, data) != NIL)
        printf("yes\n");
      else
        printf("no\n");
    }
    // delete
    else if (strcmp(str, "delete") == 0) {
      scanf("%d", &data);
      del = find(root, data);
      treedelete(del);
    }
    // print
    else if (strcmp(str, "print") == 0) {
      inorderprint(root);
      cout << endl;
      preorderprint(root);
      cout << endl;
    }
  }

  return 0;
}

Fixed submission:
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
using namespace std;
// NIL is NULL
#define NIL NULL
// Node structure
struct Node {
  int key;
  struct Node *parent;
  struct Node *leftc;
  struct Node *rightc;
};
// define Nodepointer
typedef struct Node *Nodepointer;

// root
Nodepointer root;

// function insert
void insert(int k) {
  Nodepointer x, y, z;
  y = NIL;
  x = root;
  // make memory
  z = new struct Node();

  z->key = k;
  z->leftc = NIL;
  z->rightc = NIL;

  while (x != NIL) {
    y = x;
    if (z->key < x->key)
      x = x->leftc;
    else
      x = x->rightc;
  }

  z->parent = y;

  if (y == NIL)
    root = z;

  else if (z->key < y->key)
    y->leftc = z;

  else
    y->rightc = z;
}

// function search
Nodepointer find(Nodepointer now, int data) {
  if (now == NIL || data == now->key)
    return now;
  if (data < now->key)
    return find(now->leftc, data);
  else
    return find(now->rightc, data);
}

// function treeminimum
Nodepointer treeminimum(Nodepointer x) {
  while (x->leftc != NIL) {
    x = x->leftc;
  }
  return x;
}
// function treesuccerssor
Nodepointer treesuccessor(Nodepointer x) {
  Nodepointer y;
  if (x->rightc != NIL)
    return treeminimum(x->rightc);
  y = x->parent;
  while (y != NIL && x == x->rightc) {
    x = y;
    y = y->parent;
  }
  return y;
}
// function treedelete
void treedelete(Nodepointer z) {
  Nodepointer x, y;
  if (z->leftc == NIL || z->rightc == NIL)
    y = z;
  else
    y = treesuccessor(z);

  if (y->leftc != NIL)
    x = y->leftc;
  else
    x = y->rightc;

  if (x != NIL)
    x->parent = y->parent;
  if (y->parent == NIL)
    root = x;
  else if (y == y->parent->leftc)
    y->parent->leftc = x;
  else
    y->parent->rightc = x;

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

// print
void inorderprint(Nodepointer now) {
  if (now != NIL) {
    inorderprint(now->leftc);
    printf(" %d", now->key);
    inorderprint(now->rightc);
  }
}

void preorderprint(Nodepointer now) {
  if (now != NIL) {
    printf(" %d", now->key);
    preorderprint(now->leftc);
    preorderprint(now->rightc);
  }
}

int main() {

  int n, i, j, data;
  Nodepointer del;
  char str[10];
  // load n
  scanf("%d", &n);
  // load commnad and key
  for (i = 0; i < n; i++) {
    scanf("%s", str);
    // insert
    if (strcmp(str, "insert") == 0) {
      scanf("%d", &data);
      insert(data);
    }
    // find
    else if (strcmp(str, "find") == 0) {
      scanf("%d", &data);
      if (find(root, data) != NIL)
        printf("yes\n");
      else
        printf("no\n");
    }
    // delete
    else if (strcmp(str, "delete") == 0) {
      scanf("%d", &data);
      del = find(root, data);
      treedelete(del);
    }
    // print
    else if (strcmp(str, "print") == 0) {
      inorderprint(root);
      cout << endl;
      preorderprint(root);
      cout << endl;
    }
  }

  return 0;
}