Swap kth element from the beginning and kth element from the end of linked list -- Amazon

 转载自：https://sites.google.com/site/spaceofjameschen/home

Problem

Swap kth element from the beginning and kth element from the end of linked list.

Solution

/*

 ============================================================================

 Author         : James Chen

 Email          : a.james.chen@gmail.com

 Description    : Swap kth element from the beginning and kth element from the end of linked list.

 Created Data   : 22-06-2013 

 Last Modified  :

 ============================================================================

 */

#include <iostream>

#include <iomanip>

using namespace std;

typedef struct linked_node{

    int data;

    struct linked_node *next;

}LinkedNode;

bool AddNode(LinkedNode** head, int data)

{

    LinkedNode *l = new LinkedNode;

    if(l == NULL) return false;

    

    l->data = data;

    l->next = NULL;

    if(*head == NULL){

        *head = l;

        return true;

    }

    LinkedNode* t = *head;

    while(t->next != NULL){

        t = t->next;

    }

    t->next = l;

    return true;

}

void DeleteList(LinkedNode *head)

{

    while(head != NULL){

        LinkedNode *t = head;

        head = head->next;

        delete t;

    }

}

void PrintList(LinkedNode *head)

{

    while(head != NULL){

        cout << setw(4) << head->data;

        head = head->next;

    }

    cout << endl;

}

void InitializeList(LinkedNode *head)

{

    int i = 0;

    while(head != NULL){

        head->data = i++;

        head = head->next;

    }

}

bool SwapKthNode(LinkedNode *head, int k)

{

    if(k < 1){

        cout << " k must be great than 0" << endl;

        return false;

    }

    LinkedNode *kthStart = NULL;

    LinkedNode *kthEnd = head;

    int index = 0;

    while(head != NULL){

        index ++;

        if(index == k){

            kthStart = head;

        }

        else if(index > k){

            kthEnd = kthEnd->next;

        }

        head = head->next;

    }

    

    if(index < k || kthStart == NULL){

        cout << "List length is less than " << k;

        cout << ". cannot swap 2 kth elements" << endl;

        return false;

    }

    else{

        int t = kthStart->data;

        kthStart->data = kthEnd->data;

        kthEnd->data = t;

        return true;

    }

}

void DoTest(LinkedNode *head, int k)

{

    cout << "before swapping 2 " << k << "th elements" << endl;

    PrintList(head);

    if(SwapKthNode(head, k)){

        cout << "after swapping 2 " << k << "th elements" << endl;

        PrintList(head);

    }

}

int main(int argc, char* argv[])

{

    for(int i = 1; i < 10; ++i){

        LinkedNode* head = NULL;

        for(int j = 0; j < i; ++j){

            AddNode(&head, j);

        }

        

        DoTest(head, 0);

        cout << "--------------------" << endl;

        

        InitializeList(head);

        DoTest(head, i / 2);

        cout << "--------------------" << endl;

        

        InitializeList(head);

        DoTest(head, i);

        cout << "--------------------" << endl;

        

        InitializeList(head);

        DoTest(head, i + 2);

        cout << "--------------------" << endl;

        DeleteList(head);

        cout << "=========================================" << endl;

    }

return 0;

}

Output

before swapping 2 0th elements

   0

 k must be great than 0

--------------------

before swapping 2 0th elements

   0

 k must be great than 0

--------------------

before swapping 2 1th elements

   0

after swapping 2 1th elements

   0

--------------------

before swapping 2 3th elements

   0

List length is less than 3. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1

 k must be great than 0

--------------------

before swapping 2 1th elements

   0   1

after swapping 2 1th elements

   1   0

--------------------

before swapping 2 2th elements

   0   1

after swapping 2 2th elements

   1   0

--------------------

before swapping 2 4th elements

   0   1

List length is less than 4. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2

 k must be great than 0

--------------------

before swapping 2 1th elements

   0   1   2

after swapping 2 1th elements

   2   1   0

--------------------

before swapping 2 3th elements

   0   1   2

after swapping 2 3th elements

   2   1   0

--------------------

before swapping 2 5th elements

   0   1   2

List length is less than 5. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3

 k must be great than 0

--------------------

before swapping 2 2th elements

   0   1   2   3

after swapping 2 2th elements

   0   2   1   3

--------------------

before swapping 2 4th elements

   0   1   2   3

after swapping 2 4th elements

   3   1   2   0

--------------------

before swapping 2 6th elements

   0   1   2   3

List length is less than 6. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3   4

 k must be great than 0

--------------------

before swapping 2 2th elements

   0   1   2   3   4

after swapping 2 2th elements

   0   3   2   1   4

--------------------

before swapping 2 5th elements

   0   1   2   3   4

after swapping 2 5th elements

   4   1   2   3   0

--------------------

before swapping 2 7th elements

   0   1   2   3   4

List length is less than 7. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3   4   5

 k must be great than 0

--------------------

before swapping 2 3th elements

   0   1   2   3   4   5

after swapping 2 3th elements

   0   1   3   2   4   5

--------------------

before swapping 2 6th elements

   0   1   2   3   4   5

after swapping 2 6th elements

   5   1   2   3   4   0

--------------------

before swapping 2 8th elements

   0   1   2   3   4   5

List length is less than 8. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3   4   5   6

 k must be great than 0

--------------------

before swapping 2 3th elements

   0   1   2   3   4   5   6

after swapping 2 3th elements

   0   1   4   3   2   5   6

--------------------

before swapping 2 7th elements

   0   1   2   3   4   5   6

after swapping 2 7th elements

   6   1   2   3   4   5   0

--------------------

before swapping 2 9th elements

   0   1   2   3   4   5   6

List length is less than 9. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3   4   5   6   7

 k must be great than 0

--------------------

before swapping 2 4th elements

   0   1   2   3   4   5   6   7

after swapping 2 4th elements

   0   1   2   4   3   5   6   7

--------------------

before swapping 2 8th elements

   0   1   2   3   4   5   6   7

after swapping 2 8th elements

   7   1   2   3   4   5   6   0

--------------------

before swapping 2 10th elements

   0   1   2   3   4   5   6   7

List length is less than 10. cannot swap 2 kth elements

--------------------

=========================================

before swapping 2 0th elements

   0   1   2   3   4   5   6   7   8

 k must be great than 0

--------------------

before swapping 2 4th elements

   0   1   2   3   4   5   6   7   8

after swapping 2 4th elements

   0   1   2   5   4   3   6   7   8

--------------------

before swapping 2 9th elements

   0   1   2   3   4   5   6   7   8

after swapping 2 9th elements

   8   1   2   3   4   5   6   7   0

--------------------

before swapping 2 11th elements

   0   1   2   3   4   5   6   7   8

List length is less than 11. cannot swap 2 kth elements

--------------------

=========================================

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