添加（0234.回文链表.md）：增加typescript版本

Author: xiaofei-2020

problems/0234.回文链表.md

@@ -273,7 +273,7 @@ class Solution:
         return pre
 ```
 
-## Go
+### Go
 
 ```go
 
@@ -319,6 +319,63 @@ var isPalindrome = function(head) {
 };
 ```
 
+### TypeScript
+
+> 数组模拟
+
+```typescript
+function isPalindrome(head: ListNode | null): boolean {
+    const helperArr: number[] = [];
+    let curNode: ListNode | null = head;
+    while (curNode !== null) {
+        helperArr.push(curNode.val);
+        curNode = curNode.next;
+    }
+    let left: number = 0,
+        right: number = helperArr.length - 1;
+    while (left < right) {
+        if (helperArr[left++] !== helperArr[right--]) return false;
+    }
+    return true;
+};
+```
+
+> 反转后半部分链表
+
+```typescript
+function isPalindrome(head: ListNode | null): boolean {
+    if (head === null || head.next === null) return true;
+    let fastNode: ListNode | null = head,
+        slowNode: ListNode = head,
+        preNode: ListNode = head;
+    while (fastNode !== null && fastNode.next !== null) {
+        preNode = slowNode;
+        slowNode = slowNode.next!;
+        fastNode = fastNode.next.next;
+    }
+    preNode.next = null;
+    let cur1: ListNode | null = head;
+    let cur2: ListNode | null = reverseList(slowNode);
+    while (cur1 !== null) {
+        if (cur1.val !== cur2!.val) return false;
+        cur1 = cur1.next;
+        cur2 = cur2!.next;
+    }
+    return true;
+};
+function reverseList(head: ListNode | null): ListNode | null {
+    let curNode: ListNode | null = head,
+        preNode: ListNode | null = null;
+    while (curNode !== null) {
+        let tempNode: ListNode | null = curNode.next;
+        curNode.next = preNode;
+        preNode = curNode;
+        curNode = tempNode;
+    }
+    return preNode;
+}
+```
+
 
 
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