Pairwise swap elements of a given linked list by changing links












0














Given a singly linked list, write a function to swap nodes pairwise.



For example :
**




if the linked list is 1->2->3->4->5->6->7 then the function should
change it to 2->1->4->3->6->5->7, and if the linked list is
1->2->3->4->5->6 then the function should change it to
2->1->4->3->6->5




link to the above question
**



#include <iostream>

// structure of a Node in the linked list
struct Node {
int data;
Node *next;
};

// append data to end of linked list
Node *append(Node *head, int data) {
auto newNode = new Node{data, nullptr};
if (head == nullptr)
return newNode;

auto temp{head};
while (temp->next)
temp = temp->next;
temp->next = newNode;

return head;
}

// display the list

void display(Node *head) {
std::cout << "The list : t";
while (head != nullptr) {
std::cout << head->data << " ";
head = head->next;
}
std::cout << std::endl ;
}

// pairwise swap of the elements in the given linked lists
void pairwiseSwap(Node **head_ref) {

if(((*head_ref) == nullptr) || ((*head_ref)->next == nullptr))
return ;

Node *temp1 = nullptr, *temp2 = nullptr ;
Node *prev = nullptr, *curr =(*head_ref) ;

while(curr != nullptr) {

// temp1 : first element of the pair
// temp2 : second element of the pair
temp1 = curr;
temp2 = curr->next;

// if the the 2nd element in the pair is nullptr, then exit the loop
if(temp2 == nullptr){
break ;
}
// curr = curr->next->next ;

// if the current element is head, then previous one must be nullptr
// In either case swapping the nodes
if(prev == nullptr){
prev = temp1;
temp1->next = temp2->next;
temp2->next = temp1;
(*head_ref) = temp2 ;
}
else {
temp1->next = temp2->next;
temp2->next = temp1;
prev->next = temp2;
prev = temp1;
}

// moving to the next pair of nodes
curr = temp1->next ;
}
}

// Driver function
int main() {
Node *a = nullptr ;

// for odd number of nodes
a = append(a, 15);
a = append(a, 10);
a = append(a, 5);
a = append(a, 20);
a = append(a, 3);
// a = append(a, 2);

pairwiseSwap(&a);

display(a);

// for even number of nodes
a = append(a, 15);
a = append(a, 10);
a = append(a, 5);
a = append(a, 20);
a = append(a, 3);
a = append(a, 2);

pairwiseSwap(&a);

display(a);
}








share



























    0














    Given a singly linked list, write a function to swap nodes pairwise.



    For example :
    **




    if the linked list is 1->2->3->4->5->6->7 then the function should
    change it to 2->1->4->3->6->5->7, and if the linked list is
    1->2->3->4->5->6 then the function should change it to
    2->1->4->3->6->5




    link to the above question
    **



    #include <iostream>

    // structure of a Node in the linked list
    struct Node {
    int data;
    Node *next;
    };

    // append data to end of linked list
    Node *append(Node *head, int data) {
    auto newNode = new Node{data, nullptr};
    if (head == nullptr)
    return newNode;

    auto temp{head};
    while (temp->next)
    temp = temp->next;
    temp->next = newNode;

    return head;
    }

    // display the list

    void display(Node *head) {
    std::cout << "The list : t";
    while (head != nullptr) {
    std::cout << head->data << " ";
    head = head->next;
    }
    std::cout << std::endl ;
    }

    // pairwise swap of the elements in the given linked lists
    void pairwiseSwap(Node **head_ref) {

    if(((*head_ref) == nullptr) || ((*head_ref)->next == nullptr))
    return ;

    Node *temp1 = nullptr, *temp2 = nullptr ;
    Node *prev = nullptr, *curr =(*head_ref) ;

    while(curr != nullptr) {

    // temp1 : first element of the pair
    // temp2 : second element of the pair
    temp1 = curr;
    temp2 = curr->next;

    // if the the 2nd element in the pair is nullptr, then exit the loop
    if(temp2 == nullptr){
    break ;
    }
    // curr = curr->next->next ;

    // if the current element is head, then previous one must be nullptr
    // In either case swapping the nodes
    if(prev == nullptr){
    prev = temp1;
    temp1->next = temp2->next;
    temp2->next = temp1;
    (*head_ref) = temp2 ;
    }
    else {
    temp1->next = temp2->next;
    temp2->next = temp1;
    prev->next = temp2;
    prev = temp1;
    }

    // moving to the next pair of nodes
    curr = temp1->next ;
    }
    }

    // Driver function
    int main() {
    Node *a = nullptr ;

    // for odd number of nodes
    a = append(a, 15);
    a = append(a, 10);
    a = append(a, 5);
    a = append(a, 20);
    a = append(a, 3);
    // a = append(a, 2);

    pairwiseSwap(&a);

    display(a);

    // for even number of nodes
    a = append(a, 15);
    a = append(a, 10);
    a = append(a, 5);
    a = append(a, 20);
    a = append(a, 3);
    a = append(a, 2);

    pairwiseSwap(&a);

    display(a);
    }








    share

























      0












      0








      0







      Given a singly linked list, write a function to swap nodes pairwise.



      For example :
      **




      if the linked list is 1->2->3->4->5->6->7 then the function should
      change it to 2->1->4->3->6->5->7, and if the linked list is
      1->2->3->4->5->6 then the function should change it to
      2->1->4->3->6->5




      link to the above question
      **



      #include <iostream>

      // structure of a Node in the linked list
      struct Node {
      int data;
      Node *next;
      };

      // append data to end of linked list
      Node *append(Node *head, int data) {
      auto newNode = new Node{data, nullptr};
      if (head == nullptr)
      return newNode;

      auto temp{head};
      while (temp->next)
      temp = temp->next;
      temp->next = newNode;

      return head;
      }

      // display the list

      void display(Node *head) {
      std::cout << "The list : t";
      while (head != nullptr) {
      std::cout << head->data << " ";
      head = head->next;
      }
      std::cout << std::endl ;
      }

      // pairwise swap of the elements in the given linked lists
      void pairwiseSwap(Node **head_ref) {

      if(((*head_ref) == nullptr) || ((*head_ref)->next == nullptr))
      return ;

      Node *temp1 = nullptr, *temp2 = nullptr ;
      Node *prev = nullptr, *curr =(*head_ref) ;

      while(curr != nullptr) {

      // temp1 : first element of the pair
      // temp2 : second element of the pair
      temp1 = curr;
      temp2 = curr->next;

      // if the the 2nd element in the pair is nullptr, then exit the loop
      if(temp2 == nullptr){
      break ;
      }
      // curr = curr->next->next ;

      // if the current element is head, then previous one must be nullptr
      // In either case swapping the nodes
      if(prev == nullptr){
      prev = temp1;
      temp1->next = temp2->next;
      temp2->next = temp1;
      (*head_ref) = temp2 ;
      }
      else {
      temp1->next = temp2->next;
      temp2->next = temp1;
      prev->next = temp2;
      prev = temp1;
      }

      // moving to the next pair of nodes
      curr = temp1->next ;
      }
      }

      // Driver function
      int main() {
      Node *a = nullptr ;

      // for odd number of nodes
      a = append(a, 15);
      a = append(a, 10);
      a = append(a, 5);
      a = append(a, 20);
      a = append(a, 3);
      // a = append(a, 2);

      pairwiseSwap(&a);

      display(a);

      // for even number of nodes
      a = append(a, 15);
      a = append(a, 10);
      a = append(a, 5);
      a = append(a, 20);
      a = append(a, 3);
      a = append(a, 2);

      pairwiseSwap(&a);

      display(a);
      }








      share













      Given a singly linked list, write a function to swap nodes pairwise.



      For example :
      **




      if the linked list is 1->2->3->4->5->6->7 then the function should
      change it to 2->1->4->3->6->5->7, and if the linked list is
      1->2->3->4->5->6 then the function should change it to
      2->1->4->3->6->5




      link to the above question
      **



      #include <iostream>

      // structure of a Node in the linked list
      struct Node {
      int data;
      Node *next;
      };

      // append data to end of linked list
      Node *append(Node *head, int data) {
      auto newNode = new Node{data, nullptr};
      if (head == nullptr)
      return newNode;

      auto temp{head};
      while (temp->next)
      temp = temp->next;
      temp->next = newNode;

      return head;
      }

      // display the list

      void display(Node *head) {
      std::cout << "The list : t";
      while (head != nullptr) {
      std::cout << head->data << " ";
      head = head->next;
      }
      std::cout << std::endl ;
      }

      // pairwise swap of the elements in the given linked lists
      void pairwiseSwap(Node **head_ref) {

      if(((*head_ref) == nullptr) || ((*head_ref)->next == nullptr))
      return ;

      Node *temp1 = nullptr, *temp2 = nullptr ;
      Node *prev = nullptr, *curr =(*head_ref) ;

      while(curr != nullptr) {

      // temp1 : first element of the pair
      // temp2 : second element of the pair
      temp1 = curr;
      temp2 = curr->next;

      // if the the 2nd element in the pair is nullptr, then exit the loop
      if(temp2 == nullptr){
      break ;
      }
      // curr = curr->next->next ;

      // if the current element is head, then previous one must be nullptr
      // In either case swapping the nodes
      if(prev == nullptr){
      prev = temp1;
      temp1->next = temp2->next;
      temp2->next = temp1;
      (*head_ref) = temp2 ;
      }
      else {
      temp1->next = temp2->next;
      temp2->next = temp1;
      prev->next = temp2;
      prev = temp1;
      }

      // moving to the next pair of nodes
      curr = temp1->next ;
      }
      }

      // Driver function
      int main() {
      Node *a = nullptr ;

      // for odd number of nodes
      a = append(a, 15);
      a = append(a, 10);
      a = append(a, 5);
      a = append(a, 20);
      a = append(a, 3);
      // a = append(a, 2);

      pairwiseSwap(&a);

      display(a);

      // for even number of nodes
      a = append(a, 15);
      a = append(a, 10);
      a = append(a, 5);
      a = append(a, 20);
      a = append(a, 3);
      a = append(a, 2);

      pairwiseSwap(&a);

      display(a);
      }






      c++11 linked-list





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