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17 | 17 |
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18 | 18 |
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19 | 19 | ## 解法
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20 | | -<!-- 这里可写通用的实现逻辑 --> |
| 20 | + |
| 21 | +定义指针 `p`、`q` 分别指向头节点和下一个节点,`pre` 指向头节点的前一个节点。 |
| 22 | + |
| 23 | +遍历链表,改变指针 `p` 指向的节点的指向,将其指向 `pre` 指针指向的节点,即 `p.next = pre`。然后 `pre` 指针指向 `p`,`p`、`q` 指针往前走。 |
| 24 | + |
| 25 | +当遍历结束后,返回 `pre` 指针即可。 |
21 | 26 |
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22 | 27 |
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23 | 28 | <!-- tabs:start -->
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24 | 29 |
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25 | 30 | ### **Python3**
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26 | | -<!-- 这里可写当前语言的特殊实现逻辑 --> |
27 | | - |
28 | 31 | ```python
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29 | | - |
| 32 | +# Definition for singly-linked list. |
| 33 | +# class ListNode: |
| 34 | +# def __init__(self, x): |
| 35 | +# self.val = x |
| 36 | +# self.next = None |
| 37 | + |
| 38 | +class Solution: |
| 39 | + def reverseList(self, head: ListNode) -> ListNode: |
| 40 | + pre, p = None, head |
| 41 | + while p: |
| 42 | + q = p.next |
| 43 | + p.next = pre |
| 44 | + pre = p |
| 45 | + p = q |
| 46 | + return pre |
30 | 47 | ```
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31 | 48 |
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32 | 49 | ### **Java**
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33 | | -<!-- 这里可写当前语言的特殊实现逻辑 --> |
34 | | - |
35 | 50 | ```java
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| 51 | +/** |
| 52 | + * Definition for singly-linked list. |
| 53 | + * public class ListNode { |
| 54 | + * int val; |
| 55 | + * ListNode next; |
| 56 | + * ListNode(int x) { val = x; } |
| 57 | + * } |
| 58 | + */ |
| 59 | +class Solution { |
| 60 | + public ListNode reverseList(ListNode head) { |
| 61 | + ListNode pre = null; |
| 62 | + ListNode p = head; |
| 63 | + while (p != null) { |
| 64 | + ListNode q = p.next; |
| 65 | + p.next = pre; |
| 66 | + pre = p; |
| 67 | + p = q; |
| 68 | + } |
| 69 | + return pre; |
| 70 | + } |
| 71 | +} |
| 72 | +``` |
| 73 | + |
| 74 | +### **JavaScript** |
| 75 | +```js |
| 76 | +/** |
| 77 | + * Definition for singly-linked list. |
| 78 | + * function ListNode(val) { |
| 79 | + * this.val = val; |
| 80 | + * this.next = null; |
| 81 | + * } |
| 82 | + */ |
| 83 | +/** |
| 84 | + * @param {ListNode} head |
| 85 | + * @return {ListNode} |
| 86 | + */ |
| 87 | +var reverseList = function(head) { |
| 88 | + let node = head |
| 89 | + let pre = null |
| 90 | + while(node) { |
| 91 | + let cur = node |
| 92 | + node = cur.next |
| 93 | + cur.next = pre |
| 94 | + pre = cur |
| 95 | + } |
| 96 | + return pre |
| 97 | +}; |
| 98 | +``` |
36 | 99 |
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| 100 | +### **Go** |
| 101 | + |
| 102 | +```Go |
| 103 | +func reverseList(head *ListNode) *ListNode { |
| 104 | + if head == nil ||head.Next == nil { |
| 105 | + return head |
| 106 | + } |
| 107 | + dummyHead := &ListNode{} |
| 108 | + cur := head |
| 109 | + for cur != nil { |
| 110 | + tmp := cur.Next |
| 111 | + cur.Next = dummyHead.Next |
| 112 | + dummyHead.Next = cur |
| 113 | + cur = tmp |
| 114 | + } |
| 115 | + return dummyHead.Next |
| 116 | +} |
37 | 117 | ```
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38 | 118 |
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| 119 | + |
| 120 | + |
39 | 121 | ### **...**
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| 122 | + |
40 | 123 | ```
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41 | 124 |
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42 | 125 | ```
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