[Leetcode] Swap Nodes in Pairs

最新推荐文章于 2024-10-10 01:02:39 发布

原创最新推荐文章于 2024-10-10 01:02:39 发布 · 423 阅读

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/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *swapPairs(ListNode *head) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (!head) return NULL;
        
        ListNode* prev = NULL;
        ListNode* cur = head;
        ListNode* next = NULL;
        
        while (cur)
        {
            if (cur->next)
            {
                next = cur->next;
                cur->next = next->next;
                next->next = cur;     
                if (prev)
                    prev->next = next;
                else
                    head = next;
                
                prev = cur;
                cur = cur->next;                
            }  
            else
                break;
        }
        
        return head;
    }
};

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *swapPairs(ListNode *head) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ListNode** curNext = &head;
        while (NULL != *curNext && NULL != (*curNext)->next)
        {
            ListNode* temp = (*curNext)->next;
            (*curNext)->next = (*curNext)->next->next;
            temp->next = *curNext;
            *curNext = temp;
            curNext = &(*curNext)->next->next;
        }
        
        return head;
    }
};