[LeetCode] 24. Swap Nodes in Pairs

[Animenzzzz]

Description

Given a linked list, swap every two adjacent nodes and return its head.

You may not modify the values in the list's nodes, only nodes itself may be changed.

Example:

Given 1->2->3->4, you should return the list as 2->1->4->3.

解题思路：这题比较简单，画图做好每个指针的指向就好了，别丢失了指针，这题还可用递归处理，参考 grandyang/leetcode#24

C解题：

struct ListNode* swapPairs(struct ListNode* head){
    struct ListNode* current = head;
    struct ListNode* current_prefix;
    struct ListNode* result = NULL;
    while (current)
    {
        if (!head->next) break;
        if(!result){//头结点的处理
            result = head->next;
            head->next = head->next->next;
            result->next = head;
        }else{
            if(current->next){
                current_prefix->next = current->next;
                current->next = current->next->next;
                current_prefix->next->next = current;
            }
        }
        current_prefix = current;
        current = current -> next;
    }
    if(!result) return head;
    return result;
}