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题解

迭代版

  1. /**
  2.  * Definition for singly-linked list.
  3.  * class ListNode {
  4.  *     val: number
  5.  *     next: ListNode | null
  6.  *     constructor(val?: number, next?: ListNode | null) {
  7.  *         this.val = (val===undefined ? 0 : val)
  8.  *         this.next = (next===undefined ? null : next)
  9.  *     }
  10.  * }
  11.  */
  13. function reverseBetween(head: ListNode | null, m: number, n: number): ListNode | null {
  14.     if (!head) return null;
  15.     let target = head;
  16.     let pre = null;
  17.     while (m > 1) {
  18.         pre = target;
  19.         target = target.next;
  20.         m--;
  21.         n--;
  22.     }
  23.     let a = pre;
  24.     let b = target;
  25.     while (n) {
  26.         let temp = target.next;
  27.         target.next = pre;
  28.         pre = target;
  29.         target = temp;
  30.         n--;
  31.     }
  32.     if (a) {
  33.         a.next = pre;
  34.     } else {
  35.         head = pre;
  36.     }
  37.     b.next = target;
  38.     return head;
  39. };

递归版