DAY15 Swap Nodes in Pairs

第 11 屆 iThome 鐵人賽

DAY 15

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刷題記錄與人生分享系列第 15 篇

11th鐵人賽 leetcode c javascript

keyhouse12

2019-09-16 09:39:33

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題目:

https://leetcode.com/problems/swap-nodes-in-pairs/
一個連結串列，交換2個相鄰的節點並返回首節點。

解題思路:

先用p1、p2紀錄首節點跟下一個節點，進行交換後temp用來記錄下一個要交換的節點，直到條件符合時跳出迴圈。

C版本:

struct ListNode* swapPairs(struct ListNode* head) {
    
    if (head == NULL || head -> next == NULL )
     return head;
    
    struct ListNode *p1 = head;
    struct ListNode *p2 = head -> next;
    struct ListNode *result = p2;
    struct ListNode *temp = NULL ;
    while (p1 != NULL && p2 != NULL )
    {
        p1 -> next = p2 -> next;
        p2 -> next = p1;
        
        if (temp != NULL )
                temp -> next = p2;
        temp = p1;
        if (p1 -> next != NULL && p1 -> next -> next != NULL )
            {
                p1 = p1 -> next;
                p2 = p1 -> next;
            }
            else 
                break ;
    }
    return result;
}

Javascript版本:

var swapPairs = function(head) {
    if (head == null || head.next == null )
     return head;
    var p1 = new ListNode(0);
    var p2 = new ListNode(0);
    var result = new ListNode(0);
    var temp = new ListNode(0);
    
    p1 = head;
    p2 = head.next;
    result = p2;
    temp = null;
    
    while (p1 != null && p2 != null )
    {
        p1.next = p2.next;
        p2.next = p1;
        
        if (temp != null )
            temp.next = p2;
        temp = p1;
        if (p1.next != null && p1.next.next != null )
            {
                p1 = p1.next;
                p2 = p1.next;
            }
            else 
                break ;
    }
    return result;
};