206.md

题目

给你单链表的头节点 head ，请你反转链表，并返回反转后的链表

解题思路

1. 创建节点
2. 遍历整个链表,首先保存第一个节点
3. 让接下来的节点引用前一个节点

Go语言版本

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func reverseList(head *ListNode) *ListNode {
    var prev *ListNode
    curr := head
    for curr!= nil {
        prev, curr.Next = curr.Next, prev
        prev, curr = curr, prev
    }
    return prev
}

Python语言版本

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
        curr, prev = head, None
        while curr:
            prev, prev.next, curr = curr, prev, curr.next
        return prev

C语言版本

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */


struct ListNode* reverseList(struct ListNode* head){
    struct ListNode* prev = NULL;
    struct ListNode* curr = head;
    while(curr){
        struct ListNode* temp = curr->next;
        curr->next = prev;
        prev = curr;
        curr = temp;
    }
    return prev;
}