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Zkontrolujte, zda je dvojitě propojený seznam znaků palindrom nebo ne

Vzhledem k a dvojitě propojený seznam z postavy úkolem je zkontrolovat, zda je dvojitě propojený seznam a palindrom nebo ne.

Příklady:

Vstup:



check-if-a-double-linked-list-of-characters-je-palindrom-nebo-ne' title=


výstup: Věrný
Vysvětlení: Seznam odpovídá 'LEVEL', což je palindrom.

Java vylepšená smyčka


Vstup:

check-if-a-double-linked-list-of-characters-je-palindrom-nebo-ne-2' loading='lazy' title=


výstup: Falešný
Vysvětlení: Seznam odpovídá 'LEVES', což není palindrom.

Přístup:

Cílem je inicializovat dva ukazatele: vlevo (zpočátku nastaveno na hlavu) a právo (zpočátku nastaveno na ocas). Porovnejte hodnoty dvou ukazatelů while vlevo se nerovná nule nebo vlevo se přesunul na další z právo. Pokud jsou hodnoty dvou ukazatelů rovný pohyb vlevo na další ukazatel a právo na předchozí ukazatel. Jinak vrátí false.

třídicí řetězce java

Níže je uvedena implementace výše uvedeného přístupu:

C++ 
// C++ program to check if a doubly  // linked list is palindrome. #include    using namespace std; class Node { public:  char data;  Node* prev *next;  Node (char x) {  data = x;  prev = nullptr;  next = nullptr;  } }; // Function that returns true if the // doubly linked list is a palindrome bool isPalindrome(Node* head) {  if (head == nullptr) return true;    // Find the tail ptr.  Node *left=head *right=head;  while (right->next != nullptr) {  right = right->next;  }    // Check if the doubly linked list is   // a palindrome.  while (left!=right && left->prev!=right) {    // If char mismatch return  // false.  if (left->data != right->data)  return false;    // Move the pointers  left = left->next;  right = right->prev;  }    return true; } int main() {    // Doubly Linked list:   // L <-> E <-> V <-> E <-> L  Node *head = new Node('L');  head->next = new Node('E');  head->next->prev = head;  head->next->next = new Node('V');  head->next->next->prev = head->next;  head->next->next->next = new Node('E');  head->next->next->next->prev = head->next->next;  head->next->next->next->next = new Node('L');  head->next->next->next->next->prev = head->next->next->next;  if (isPalindrome(head))  cout << 'True';  else  cout << 'False';  return 0; }
C 
// C program to check if a doubly  // linked list is palindrome. #include  #include  struct Node {  char data;  struct Node* prev;  struct Node* next; }; // Function that returns true if the // doubly linked list is a palindrome int isPalindrome(struct Node* head) {  if (head == NULL) return 1;    // Find the tail ptr.  struct Node *left = head *right = head;  while (right->next != NULL) {  right = right->next;  }    // Check if the doubly linked list is   // a palindrome.  while (left != right && left->prev != right) {    // If char mismatch return  // false.  if (left->data != right->data)  return 0;    // Move the pointers  left = left->next;  right = right->prev;  }    return 1; } struct Node* createNode(char x) {  struct Node* newNode =   (struct Node*)malloc(sizeof(struct Node));  newNode->data = x;  newNode->prev = NULL;  newNode->next = NULL;  return newNode; } int main() {    // Doubly Linked list:   // L <-> E <-> V <-> E <-> L  struct Node *head = createNode('L');  head->next = createNode('E');  head->next->prev = head;  head->next->next = createNode('V');  head->next->next->prev = head->next;  head->next->next->next = createNode('E');  head->next->next->next->prev = head->next->next;  head->next->next->next->next = createNode('L');  head->next->next->next->next->prev = head->next->next->next;  if (isPalindrome(head))  printf('Truen');  else  printf('Falsen');  return 0; }
Java 
// Java program to check if a doubly  // linked list is palindrome. class Node {  char data;  Node prev next;  Node(char x) {  data = x;  prev = null;  next = null;  } } class GfG {  // Function that returns true if the  // doubly linked list is a palindrome  static boolean isPalindrome(Node head) {  if (head == null) return true;    // Find the tail ptr.  Node left = head right = head;  while (right.next != null) {  right = right.next;  }    // Check if the doubly linked list is   // a palindrome.  while (left != right && left.prev != right) {    // If char mismatch return  // false.  if (left.data != right.data)  return false;    // Move the pointers  left = left.next;  right = right.prev;  }    return true;  }  public static void main(String[] args) {  // Doubly Linked list:   // L <-> E <-> V <-> E <-> L  Node head = new Node('L');  head.next = new Node('E');  head.next.prev = head;  head.next.next = new Node('V');  head.next.next.prev = head.next;  head.next.next.next = new Node('E');  head.next.next.next.prev = head.next.next;  head.next.next.next.next = new Node('L');  head.next.next.next.next.prev = head.next.next.next;  if (isPalindrome(head))  System.out.println('True');  else  System.out.println('False');  } }
Python 
# Python program to check if a doubly  # linked list is palindrome. class Node: def __init__(self x): self.data = x self.prev = None self.next = None # Function that returns true if the # doubly linked list is a palindrome def isPalindrome(head): if head is None: return True # Find the tail ptr. left = head right = head while right.next is not None: right = right.next # Check if the doubly linked list is  # a palindrome. while left != right and left.prev != right: # If char mismatch return # false. if left.data != right.data: return False # Move the pointers left = left.next right = right.prev return True if __name__ == '__main__': # Doubly Linked list:  # L <-> E <-> V <-> E <-> L head = Node('L') head.next = Node('E') head.next.prev = head head.next.next = Node('V') head.next.next.prev = head.next head.next.next.next = Node('E') head.next.next.next.prev = head.next.next head.next.next.next.next = Node('L') head.next.next.next.next.prev = head.next.next.next if isPalindrome(head): print('True') else: print('False')
C# 
// C# program to check if a doubly  // linked list is palindrome. using System; class Node {  public char data;  public Node prev next;  public Node(char x) {  data = x;  prev = null;  next = null;  } } class GfG {  // Function that returns true if the  // doubly linked list is a palindrome  static bool isPalindrome(Node head) {  if (head == null) return true;    // Find the tail ptr.  Node left = head right = head;  while (right.next != null) {  right = right.next;  }    // Check if the doubly linked list is   // a palindrome.  while (left != right && left.prev != right) {    // If char mismatch return  // false.  if (left.data != right.data)  return false;    // Move the pointers  left = left.next;  right = right.prev;  }    return true;  }  static void Main(string[] args) {  // Doubly Linked list:   // L <-> E <-> V <-> E <-> L  Node head = new Node('L');  head.next = new Node('E');  head.next.prev = head;  head.next.next = new Node('V');  head.next.next.prev = head.next;  head.next.next.next = new Node('E');  head.next.next.next.prev = head.next.next;  head.next.next.next.next = new Node('L');  head.next.next.next.next.prev = head.next.next.next;    if (isPalindrome(head))  Console.WriteLine('True');  else  Console.WriteLine('False');  } }
JavaScript 
// JavaScript program to check if a doubly  // linked list is palindrome. class Node {  constructor(x) {  this.data = x;  this.prev = null;  this.next = null;  } } // Function that returns true if the // doubly linked list is a palindrome function isPalindrome(head) {  if (head === null) return true;    // Find the tail ptr.  let left = head right = head;  while (right.next !== null) {  right = right.next;  }    // Check if the doubly linked list is   // a palindrome.  while (left !== right && left.prev !== right) {    // If char mismatch return  // false.  if (left.data !== right.data)  return false;    // Move the pointers  left = left.next;  right = right.prev;  }    return true; } // Doubly Linked list:  // L <-> E <-> V <-> E <-> L let head = new Node('L'); head.next = new Node('E'); head.next.prev = head; head.next.next = new Node('V'); head.next.next.prev = head.next; head.next.next.next = new Node('E'); head.next.next.next.prev = head.next.next; head.next.next.next.next = new Node('L'); head.next.next.next.next.prev = head.next.next.next; if (isPalindrome(head))  console.log('True'); else  console.log('False');

Výstup 
True

Časová složitost: O(n) kde n je počet uzlů ve dvojitě propojeném seznamu.
Pomocný prostor: O(1)

Související články:   

  • Funkce pro kontrolu, zda je jednotlivě propojený seznam palindrom
  • Zkontrolujte, zda propojený seznam řetězců tvoří palindrom
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