将最后一个元素移动到给定链表的前面 | 2套

给定一个单向链表和一个整数K 。任务是将链表的最后 K 个元素追加到前面。

例子：

Input: 1 -> 2 -> 3 -> 4 -> 5 -> 6, k = 3
Output : 4 -> 5 -> 6 -> 1 -> 2 -> 3

Input: 1 -> 2 -> 3 -> 4 -> 5 -> 6, k = 7
Output : 6 -> 1 -> 2 -> 3 -> 4 -> 5

先决条件：将最后一个元素移动到给定链表的前面

方法：

• 循环 (k % n) 次，其中 n 是链表的元素数。
• 每次从链表的末尾删除一个节点。
• 同时在链表的开头插入删除的节点。

  下面是上述方法的实现：

  // CPP Program to move k last elements 
  // to front in a given linked list 
  #include
  using namespace std;
    
  // A linked list node 
  class Node
  {
      public:
        
      int data;
      Node* next;
      Node(int d) {
          data = d;
          next = NULL;
      }
  };
    
  // Function to add a new node at the
  // end/tail of Linked List 
  void insertAtTail(Node*& head, Node*& tail, int d ) {
      Node* newnode = new Node(d);
      if(tail == NULL) {
          tail = head = newnode;
          return;
      }
    
      tail->next = newnode;
      tail = newnode;
  }
    
  // Function to add a node at the
  // beginning of Linked List 
  void insertAtHead(Node*& head, Node*& tail, 
                             Node*& deletedNode) 
  {
      if(head == NULL) {
          head = tail = deletedNode;
          return;
      }
      deletedNode->next = head;
      head = deletedNode;
      return;
  }
    
  // Function to add a node at the beginning of Linked List 
  Node* deleteAtTail(Node*& head, Node*& tail) {
      Node* deleted = tail;
      Node* temp = head;
    
      while(temp->next->next != NULL) {
          temp = temp->next;
      }
    
      temp->next = NULL;
      tail = temp;
      return deleted;
  }
    
  // k can be more than n, so this function takes the modulus 
  // of k with n and delete nodes from end k 
  // times and simultaneously insert it in front
  void appendAtFront(Node*& head, Node*& tail, int n, int k) 
  {
      k = k % n;
      while(k != 0) {
          Node* deleted = deleteAtTail(head, tail);
          insertAtHead(head, tail, deleted);
          k--;
      }
  }
    
  // Function to print nodes in a given linked list 
  void printLinkedList(Node* head) {
      while(head != NULL) {
          cout << head->data << " ";
          head = head->next;
      }
      cout << endl;
  }
    
  // Driver Code 
  int main() 
  {
      // Pointer to the start of the linked list
      Node* head = NULL;
        
      // Pointer to the end of the linked list
      Node* tail = NULL; 
        
      // Number of elements in the linked list
      int n = 6; 
        
      // Building linked list
      insertAtTail(head, tail, 1);
      insertAtTail(head, tail, 2);
      insertAtTail(head, tail, 3);
      insertAtTail(head, tail, 4);
      insertAtTail(head, tail, 5);
      insertAtTail(head, tail, 6);
        
        
      // Printing linked list before 
      // appending the linked list
      cout << "Linked List before appending: ";
      printLinkedList(head);
        
      // Number of elements to be appended
      int k = 7;
        
      // Function call
      appendAtFront(head, tail, n, k); 
        
      // Printing linked list after appending the list
      cout << "Linked List after appending "<

  输出：

  Linked List before appending: 1 2 3 4 5 6 
  Linked List after appending 7 elements: 6 1 2 3 4 5 
  

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