codingMan1216
diff --git a/‎125. Reorder List/README.md
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diff --git a/‎125. Reorder List/main.cpp
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diff --git a/‎125. Reorder List/solution.h
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+举例：
+
+    1->2->3->4->5->6->7->8
+
+要求重排为：
+
+    1->8->2->7->3->6->4->5
+
+看似摸不着头绪，单链表的最大问题不就是没法走回头路吗？
+
+但如果我们将链表切成两部分呢？
+
+    1->2->3->4
+    5->6->7->8
+
+然后回忆一下链表基本操作，咦，是否将第二个链表逆序一下即可？
+
+    1->2->3->4
+    8->7->6->5
+
+到了这一步，差不多真相大白了吧。两个链表合并，貌似没一点难度。
+
+------
+
+**具体技术**
+
+逆序的技巧不需多说，切成两部分，关键是找中点，这个可以利用我们常用的技巧：快慢指针。
+
+    1->2->3->4->5->6->7->8->null
+    ^  ^  ^  ^  ^  ^  ^  ^  ^
+    s  f  |  |  |  |  |  |  |
+    s  |  f  |  |  |  |  |  |
+       s  |  f  |  |  |  |  |
+       s  |  |  f  |  |  |  |
+          s  |     f  |  |  |
+          s  |        f  |  |
+             s           f  |
+             s              f
+
+可以看到，`s` 正好停在指向 `4` 的地方。
+
+逆序之后，链表应呈现以下情形：
+
+    1->2->3->4->8->7->6->5->null
+    ^        ^
+    head     slow
+
+再进一步，将该链表分为两个：
+
+    1->2->3->4->null
+    8->7->6->5->null
+
+然后用咱们现成的 `shuffleMerge` 即可。
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+#include "solution.h"
+#include <iostream>
+#include <initializer_list>
+using namespace std;
+
+ListNode *create_linkedlist(std::initializer_list<int> lst)
+{
+    auto iter = lst.begin();
+    ListNode *head = lst.size() ? new ListNode(*iter++) : nullptr;
+    for (ListNode *cur=head; iter != lst.end(); cur=cur->next)
+        cur->next = new ListNode(*iter++);
+    return head;
+}
+
+void clear(ListNode *head)
+{
+    while (head) {
+        ListNode *del = head;
+        head = head->next;
+        delete del;
+    }
+}
+
+void printList(ListNode *head) {
+    for (ListNode *cur = head; cur; cur = cur->next)
+        cout << cur->val << "->";
+    cout << "\b\b  " << endl;
+}
+
+int main()
+{
+    Solution s;
+    ListNode *a = create_linkedlist({1,2,3,4,5,6,7,8,9});
+    s.reorderList(a);
+    printList(a);
+    clear(a);
+}
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+#include <cstddef>
+
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode(int x) : val(x), next(NULL) {}
+};
+
+class Solution {
+    ListNode* reverseList(ListNode *head) {
+        ListNode *newHead = NULL;
+        while (head) {
+            ListNode *next = head->next;
+            head->next = newHead;
+            newHead = head;
+            head = next;
+        }
+        return newHead;
+    }
+
+    ListNode *shuffleMerge(ListNode *a, ListNode *b) {
+        ListNode *ret = NULL, **lastRef = &ret;
+        while (a && b) {
+            moveNode(lastRef, &a);
+            lastRef = &((*lastRef)->next);
+            moveNode(lastRef, &b);
+            lastRef = &((*lastRef)->next);
+        }
+        *lastRef = a ? a : b;
+        return ret;
+    }
+
+    void moveNode(ListNode **destRef, ListNode **sourceRef) {
+        ListNode *newNode = *sourceRef;
+        *sourceRef = newNode->next;
+        newNode->next = *destRef;
+        *destRef = newNode;
+    }
+
+public:
+    void reorderList(ListNode *head) {
+        if (head == NULL) return;
+        ListNode *slow = head, *fast = head->next;
+        while (fast) {
+            fast = fast->next;
+            if (fast) {
+                slow = slow->next;
+                fast = fast->next;
+            }
+        }
+        ListNode *back = reverseList(slow->next);
+        slow->next = NULL;
+        head = shuffleMerge(head, back);
+    }
+};