力扣：92. 反转链表 II

LeetCode/src/main/java/com/code/leet/study/t20210209/ReverseBetween.java

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+package com.code.leet.study.t20210209;
+
+import com.code.leet.entiy.ListNode;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * 反转从位置 m 到 n 的链表。请使用一趟扫描完成反转。
+ * <p>
+ * 说明:
+ * 1 ≤ m ≤ n ≤ 链表长度。
+ */
+public class ReverseBetween {
+    /**
+     * 92. 反转链表 II
+     */
+    public ListNode reverseBetween(ListNode head, int m, int n) {
+        if (n == 1) {
+            return head;
+        }
+        List<ListNode> list = new ArrayList<>();
+        int num = 1;
+        ListNode before = new ListNode(0);
+        ListNode after = null;
+        ListNode temp = head;
+        while (temp != null) {
+            if (num == m - 1) {
+                before = temp;
+            }
+            if (num >= m && num <= n) {
+                list.add(temp);
+            }
+            if (num == n) {
+                after = temp.next;
+                break;
+            }
+            temp = temp.next;
+            num++;
+        }
+        ListNode newHead = before;
+        int size = list.size();
+        for (int i = size - 1; i >= 0; i--) {
+            before.next = list.get(i);
+            before = before.next;
+        }
+        before.next = after;
+        if (m == 1) {
+            head = newHead.next;
+        }
+        return head;
+    }
+}