diff --git a/leetcode/index.md b/leetcode/index.md
new file mode 100644
index 00000000..1f10b479
--- /dev/null
+++ b/leetcode/index.md
@@ -0,0 +1,3 @@
+# leetcode 问题列表
+
+这一章节, 分别基于问题所属的标签, 和问题编号, 列出问题, 方便索引.
\ No newline at end of file
diff --git a/leetcode/orders/0001-0100.md b/leetcode/orders/0001-0100.md
new file mode 100644
index 00000000..96f7220f
--- /dev/null
+++ b/leetcode/orders/0001-0100.md
@@ -0,0 +1,2 @@
+# 问题 0001-0100
+
diff --git a/leetcode/orders/0101-0200.md b/leetcode/orders/0101-0200.md
new file mode 100644
index 00000000..1d1a1aef
--- /dev/null
+++ b/leetcode/orders/0101-0200.md
@@ -0,0 +1,2 @@
+# 问题 0101-0200
+
diff --git a/leetcode/orders/0201-0300.md b/leetcode/orders/0201-0300.md
new file mode 100644
index 00000000..03ad57ab
--- /dev/null
+++ b/leetcode/orders/0201-0300.md
@@ -0,0 +1,2 @@
+# 问题 0201-0300
+
diff --git a/leetcode/orders/0301-0400.md b/leetcode/orders/0301-0400.md
new file mode 100644
index 00000000..e8d9bd6e
--- /dev/null
+++ b/leetcode/orders/0301-0400.md
@@ -0,0 +1,2 @@
+# 问题 0301-0400
+
diff --git a/leetcode/orders/0401-0500.md b/leetcode/orders/0401-0500.md
new file mode 100644
index 00000000..bc6b9294
--- /dev/null
+++ b/leetcode/orders/0401-0500.md
@@ -0,0 +1 @@
+# 问题 0401-0500
\ No newline at end of file
diff --git a/leetcode/orders/0501-0600.md b/leetcode/orders/0501-0600.md
new file mode 100644
index 00000000..679d3865
--- /dev/null
+++ b/leetcode/orders/0501-0600.md
@@ -0,0 +1 @@
+# 问题 0501-0600
\ No newline at end of file
diff --git a/leetcode/orders/0601-0700.md b/leetcode/orders/0601-0700.md
new file mode 100644
index 00000000..3347bc98
--- /dev/null
+++ b/leetcode/orders/0601-0700.md
@@ -0,0 +1 @@
+# 问题 0601-0700
\ No newline at end of file
diff --git a/leetcode/orders/0701-0800.md b/leetcode/orders/0701-0800.md
new file mode 100644
index 00000000..f49cee5a
--- /dev/null
+++ b/leetcode/orders/0701-0800.md
@@ -0,0 +1 @@
+# 问题 0701-0800
\ No newline at end of file
diff --git a/leetcode/orders/0801-0900.md b/leetcode/orders/0801-0900.md
new file mode 100644
index 00000000..5bc6d993
--- /dev/null
+++ b/leetcode/orders/0801-0900.md
@@ -0,0 +1 @@
+# 问题 0801-0900
\ No newline at end of file
diff --git a/leetcode/orders/0901-1000.md b/leetcode/orders/0901-1000.md
new file mode 100644
index 00000000..68d20d34
--- /dev/null
+++ b/leetcode/orders/0901-1000.md
@@ -0,0 +1 @@
+# 问题 0901-1000
\ No newline at end of file
diff --git a/leetcode/orders/1001-1100.md b/leetcode/orders/1001-1100.md
new file mode 100644
index 00000000..d5c57929
--- /dev/null
+++ b/leetcode/orders/1001-1100.md
@@ -0,0 +1 @@
+# 问题 1001-1100
\ No newline at end of file
diff --git a/leetcode/orders/1101-1200.md b/leetcode/orders/1101-1200.md
new file mode 100644
index 00000000..f48ca8af
--- /dev/null
+++ b/leetcode/orders/1101-1200.md
@@ -0,0 +1 @@
+# 问题 1101-1200
\ No newline at end of file
diff --git a/leetcode/orders/1201-1300.md b/leetcode/orders/1201-1300.md
new file mode 100644
index 00000000..2d3e7a43
--- /dev/null
+++ b/leetcode/orders/1201-1300.md
@@ -0,0 +1 @@
+# 问题 1201-1300
\ No newline at end of file
diff --git a/leetcode/orders/1301-1400.md b/leetcode/orders/1301-1400.md
new file mode 100644
index 00000000..e6a23e88
--- /dev/null
+++ b/leetcode/orders/1301-1400.md
@@ -0,0 +1 @@
+# 问题 1301-1400
\ No newline at end of file
diff --git a/leetcode/orders/1401-1500.md b/leetcode/orders/1401-1500.md
new file mode 100644
index 00000000..cd07e32e
--- /dev/null
+++ b/leetcode/orders/1401-1500.md
@@ -0,0 +1 @@
+# 问题 1401-1500
\ No newline at end of file
diff --git a/leetcode/orders/1501-1600.md b/leetcode/orders/1501-1600.md
new file mode 100644
index 00000000..c6f7571f
--- /dev/null
+++ b/leetcode/orders/1501-1600.md
@@ -0,0 +1,2 @@
+# 问题 1501-1600
+
diff --git a/leetcode/orders/1601-1700.md b/leetcode/orders/1601-1700.md
new file mode 100644
index 00000000..2a7e6218
--- /dev/null
+++ b/leetcode/orders/1601-1700.md
@@ -0,0 +1 @@
+# 问题 1601-1700
\ No newline at end of file
diff --git a/leetcode/orders/1701-1800.md b/leetcode/orders/1701-1800.md
new file mode 100644
index 00000000..1addfb6c
--- /dev/null
+++ b/leetcode/orders/1701-1800.md
@@ -0,0 +1,2 @@
+# 问题 1701-1800
+
diff --git a/leetcode/orders/1801-1900.md b/leetcode/orders/1801-1900.md
new file mode 100644
index 00000000..e80ec8f4
--- /dev/null
+++ b/leetcode/orders/1801-1900.md
@@ -0,0 +1 @@
+# 问题 1801-1900
\ No newline at end of file
diff --git a/leetcode/orders/1901-2000.md b/leetcode/orders/1901-2000.md
new file mode 100644
index 00000000..3911b2eb
--- /dev/null
+++ b/leetcode/orders/1901-2000.md
@@ -0,0 +1 @@
+# 问题 1901-2000
\ No newline at end of file
diff --git a/leetcode/orders/2101-2200.md b/leetcode/orders/2101-2200.md
new file mode 100644
index 00000000..b2efd714
--- /dev/null
+++ b/leetcode/orders/2101-2200.md
@@ -0,0 +1,2 @@
+# 问题 2101-2200
+
diff --git a/leetcode/problems/index.md b/leetcode/problems/index.md
deleted file mode 100644
index e8289725..00000000
--- a/leetcode/problems/index.md
+++ /dev/null
@@ -1,20 +0,0 @@
-# 第三部分: 所有问题
-
-列出所有 leetcode 问题.
-
-- [0001. 两数之和 Two Sum](0001.two-sum/content.html)
-- [0007. 整数反转 Reverse Integer](0007.reverse-integer/content.html)
-- [0026. 删除有序数组中的重复项 Remove Duplicates from Sorted Array](0026.remove-duplicates-from-sorted-array/content.html)
-- [0067. 二进制求和 Add Binary](0067.add-binary/content.html)
-- [0136. 只出现一次的数字 Single Number](0136.single-number/content.html)
-- [0137. 只出现一次的数字II Single Number II](0137.single-number-ii/content.html)
-- [0191. 位1的个数 Number of 1 Bits](0191.number-of-1-bits/content.html)
-- [0217. 存在重复元素 Contains Duplicate](0217.contains-duplicate/content.html)
-- [0219. 存在重复元素II Contains Duplicate II](0219.contains-duplicate-ii/content.html)
-- [0231. 2的幂 Power of Two](0231.power-of-two/content.html)
-- [0326. 3的幂 Power of Three](0326.power-of-three/content.html)
-- [0338. 比特位计数 Counting Bits](0338.counting-bits/content.html)
-- [0342. 4的幂 Power of Four](0342.power-of-four/content.html)
-- [1518. 换水问题 Water Bottles](1518.water-bottles/content.html)
-- [1780. 判断一个数字是否可以表示成三的幂的和 Check if Number is a Sum of Powers of Three](1780.check-if-number-is-a-sum-of-powers-of-three/content.html)
-- [2119. 反转两次的数字 A Number After a Double Reversal](2119.a-number-after-a-double-reversal/content.html)
diff --git a/src/array/problems.md b/leetcode/tags/array.md
similarity index 100%
rename from src/array/problems.md
rename to leetcode/tags/array.md
diff --git a/src/backtracking/problems.md b/leetcode/tags/backtracking.md
similarity index 100%
rename from src/backtracking/problems.md
rename to leetcode/tags/backtracking.md
diff --git a/src/leetcode/tags/binary-search.md b/leetcode/tags/binary-search.md
similarity index 100%
rename from src/leetcode/tags/binary-search.md
rename to leetcode/tags/binary-search.md
diff --git a/src/leetcode/tags/bit-manipulation.md b/leetcode/tags/bit-manipulation.md
similarity index 100%
rename from src/leetcode/tags/bit-manipulation.md
rename to leetcode/tags/bit-manipulation.md
diff --git a/src/leetcode/tags/dynamic-programming.md b/leetcode/tags/dynamic-programming.md
similarity index 100%
rename from src/leetcode/tags/dynamic-programming.md
rename to leetcode/tags/dynamic-programming.md
diff --git a/src/leetcode/tags/graph.md b/leetcode/tags/graph.md
similarity index 100%
rename from src/leetcode/tags/graph.md
rename to leetcode/tags/graph.md
diff --git a/src/leetcode/tags/greedy-algs.md b/leetcode/tags/greedy-algs.md
similarity index 100%
rename from src/leetcode/tags/greedy-algs.md
rename to leetcode/tags/greedy-algs.md
diff --git a/src/leetcode/tags/hash-table.md b/leetcode/tags/hash-table.md
similarity index 100%
rename from src/leetcode/tags/hash-table.md
rename to leetcode/tags/hash-table.md
diff --git a/src/leetcode/tags/index.md b/leetcode/tags/index.md
similarity index 100%
rename from src/leetcode/tags/index.md
rename to leetcode/tags/index.md
diff --git a/src/leetcode/tags/linked-list.md b/leetcode/tags/linked-list.md
similarity index 100%
rename from src/leetcode/tags/linked-list.md
rename to leetcode/tags/linked-list.md
diff --git a/leetcode/tags/math.md b/leetcode/tags/math.md
new file mode 100644
index 00000000..1cf3b7e2
--- /dev/null
+++ b/leetcode/tags/math.md
@@ -0,0 +1,13 @@
+# 数学问题的问题列表
+
+## 简单
+
+- [2119. 反转两次的数字 A Number After a Double Reversal](../2119.a-number-after-a-double-reversal/index.md)
+- [1518. 换水问题 Water Bottles](../1518.water-bottles/index.md)
+
+## 中等
+
+- [0007. 整数反转 Reverse Integer](../0007.reverse-integer/index.md)
+- [1780. 判断一个数字是否可以表示成三的幂的和 Check if Number is a Sum of Powers of Three](../1780.check-if-number-is-a-sum-of-powers-of-three/index.md)
+
+- [3100. Water Bottles II](https://leetcode.com/problems/water-bottles-ii)
\ No newline at end of file
diff --git a/src/leetcode/tags/sliding-window.md b/leetcode/tags/sliding-window.md
similarity index 100%
rename from src/leetcode/tags/sliding-window.md
rename to leetcode/tags/sliding-window.md
diff --git a/src/leetcode/tags/stack.md b/leetcode/tags/stack.md
similarity index 100%
rename from src/leetcode/tags/stack.md
rename to leetcode/tags/stack.md
diff --git a/src/leetcode/tags/string.md b/leetcode/tags/string.md
similarity index 100%
rename from src/leetcode/tags/string.md
rename to leetcode/tags/string.md
diff --git a/src/leetcode/tags/tree.md b/leetcode/tags/tree.md
similarity index 100%
rename from src/leetcode/tags/tree.md
rename to leetcode/tags/tree.md
diff --git a/src/leetcode/tags/two-pointers.md b/leetcode/tags/two-pointers.md
similarity index 100%
rename from src/leetcode/tags/two-pointers.md
rename to leetcode/tags/two-pointers.md
diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index 8a026976..613afe5e 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -3,7 +3,7 @@
 - [简介](introduction/index.md)
 - [第一部分: 数据结构](ds/index.md)
 - [数组 Arrays](array/index.md)
-    - [数组相关的问题列表](array/problems.md)
+    - [数组相关的问题列表](leetcode/tags/array.md)
 - [动态数组 Vector](vector/index.md)
 - [双端队列 Deque](deque/index.md)
 - [链表](list/index.md)
@@ -63,7 +63,7 @@
 - [滑动窗口 Sliding Window](sliding-window/index.md)
     - [滑动窗口相关的问题列表](leetcode/tags/sliding-window.md)
 - [回溯法 Backtracking](backtracking/index.md)
-    - [回溯法相关的问题列表](backtracking/problems.md)
+    - [回溯法相关的问题列表](leetcode/tags/backtracking.md)
 - [分治法 Divide and Conquer](divide-and-conquer/index.md)
 - [动态规划 Dynamic Programming](dynamic-programming/index.md)
     - [动态规划相关的问题列表](leetcode/tags/dynamic-programming.md)
@@ -72,8 +72,55 @@
 - [第三部分: 扩展主题](extras/index.md)
     - [内存](extras/memory/index.md)
 - [leetcode 问题列表](leetcode/index.md)
-    - [分类标签](leetcode/tags/index.md)
-    - [问题 0001-0100](leetcode/0001-0100.md)
-    - [问题 0101-0200](leetcode/0101-0200.md)
-    - [问题 0201-0300](leetcode/0201-0300.md)
+    - [数组](leetcode/tags/array.md)
+    - [二分查找](leetcode/tags/binary-search.md)
+    - [位运算](leetcode/tags/bit-manipulation.md)
+    - [回溯法](leetcode/tags/backtracking.md)
+    - [动态规划](leetcode/tags/dynamic-programming.md)
+    - [图](leetcode/tags/graph.md)
+    - [贪心算法](leetcode/tags/greedy-algs.md)
+    - [哈稀表](leetcode/tags/hash-table.md)
+    - [链表](leetcode/tags/linked-list.md)
+    - [数学](leetcode/tags/math.md)
+    - [滑动窗口](leetcode/tags/sliding-window.md)
+    - [栈](leetcode/tags/stack.md)
+    - [字符串](leetcode/tags/string.md)
+    - [树](leetcode/tags/tree.md)
+    - [0001-0100](leetcode/orders/0001-0100.md)
+        - [0001. 两数之和 Two Sum](leetcode/0001.two-sum/index.md)
+        - [0007. 整数反转 Reverse Integer](leetcode/0007.reverse-integer/index.md)
+        - [0026. 删除有序数组中的重复项 Remove Duplicates from Sorted Array](leetcode/0026.remove-duplicates-from-sorted-array/index.md)
+        - [0067. 二进制求和 Add Binary](leetcode/0067.add-binary/index.md)
+    - [0101-0200](leetcode/orders/0101-0200.md)
+        - [0136. 只出现一次的数字 Single Number](leetcode/0136.single-number/index.md)
+        - [0137. 只出现一次的数字II Single Number II](leetcode/0137.single-number-ii/index.md)
+        - [0191. 位1的个数 Number of 1 Bits](leetcode/0191.number-of-1-bits/index.md)
+    - [0201-0300](leetcode/orders/0201-0300.md)
+        - [0217. 存在重复元素 Contains Duplicate](leetcode/0217.contains-duplicate/index.md)
+        - [0219. 存在重复元素II Contains Duplicate II](leetcode/0219.contains-duplicate-ii/index.md)
+        - [0231. 2的幂 Power of Two](leetcode/0231.power-of-two/index.md)
+    - [0301-0400](leetcode/orders/0301-0400.md)
+        - [0326. 3的幂 Power of Three](leetcode/0326.power-of-three/index.md)
+        - [0338. 比特位计数 Counting Bits](leetcode/0338.counting-bits/index.md)
+        - [0342. 4的幂 Power of Four](leetcode/0342.power-of-four/index.md)
+    - [0401-0500](leetcode/orders/0401-0500.md)
+    - [0501-0600](leetcode/orders/0501-0600.md)
+    - [0601-0700](leetcode/orders/0601-0700.md)
+    - [0701-0800](leetcode/orders/0701-0800.md)
+    - [0801-0900](leetcode/orders/0801-0900.md)
+    - [0901-1000](leetcode/orders/0901-1000.md)
+    - [1001-1100](leetcode/orders/1001-1100.md)
+    - [1101-1200](leetcode/orders/1101-1200.md)
+    - [1201-1300](leetcode/orders/1201-1300.md)
+    - [1301-1400](leetcode/orders/1301-1400.md)
+    - [1401-1500](leetcode/orders/1401-1500.md)
+    - [1501-1600](leetcode/orders/1501-1600.md)
+        - [1518. 换水问题 Water Bottles](leetcode/1518.water-bottles/index.md)
+    - [1601-1700](leetcode/orders/1601-1700.md)
+    - [1701-1800](leetcode/orders/1701-1800.md)
+        - [1780. 判断一个数字是否可以表示成三的幂的和 Check if Number is a Sum of Powers of Three](leetcode/1780.check-if-number-is-a-sum-of-powers-of-three/index.md)
+    - [1801-1900](leetcode/orders/1801-1900.md)
+    - [1901-2000](leetcode/orders/1901-2000.md)
+    - [2101-2200](leetcode/orders/2101-2200.md)
+        - [2119. 反转两次的数字 A Number After a Double Reversal](leetcode/2119.a-number-after-a-double-reversal/index.md)
 - [参考资料](refs.md)
diff --git a/src/leetcode b/src/leetcode
new file mode 120000
index 00000000..9c6192e9
--- /dev/null
+++ b/src/leetcode
@@ -0,0 +1 @@
+../leetcode/
\ No newline at end of file
diff --git a/src/leetcode/0001-0100.md b/src/leetcode/0001-0100.md
deleted file mode 100644
index b9b38ea4..00000000
--- a/src/leetcode/0001-0100.md
+++ /dev/null
@@ -1 +0,0 @@
-# 问题 0001-0100
\ No newline at end of file
diff --git a/src/leetcode/0101-0200.md b/src/leetcode/0101-0200.md
deleted file mode 100644
index 64fde5fc..00000000
--- a/src/leetcode/0101-0200.md
+++ /dev/null
@@ -1 +0,0 @@
-# 问题 0101-0200
\ No newline at end of file
diff --git a/src/leetcode/0201-0300.md b/src/leetcode/0201-0300.md
deleted file mode 100644
index fbdaf876..00000000
--- a/src/leetcode/0201-0300.md
+++ /dev/null
@@ -1 +0,0 @@
-# 问题 0201-0300
\ No newline at end of file
diff --git a/src/leetcode/index.md b/src/leetcode/index.md
deleted file mode 100644
index 15ab5ebd..00000000
--- a/src/leetcode/index.md
+++ /dev/null
@@ -1,19 +0,0 @@
-# leetcode 问题列表
-
-- [第二部分: 所有问题的答案](solutions.md)
-    - [0001. 两数之和 Two Sum](0001.two-sum/index.md)
-    - [0007. 整数反转 Reverse Integer](0007.reverse-integer/index.md)
-    - [0026. 删除有序数组中的重复项 Remove Duplicates from Sorted Array](0026.remove-duplicates-from-sorted-array/index.md)
-    - [0067. 二进制求和 Add Binary](0067.add-binary/index.md)
-    - [0136. 只出现一次的数字 Single Number](0136.single-number/index.md)
-    - [0137. 只出现一次的数字II Single Number II](0137.single-number-ii/index.md)
-    - [0191. 位1的个数 Number of 1 Bits](0191.number-of-1-bits/index.md)
-    - [0217. 存在重复元素 Contains Duplicate](0217.contains-duplicate/index.md)
-    - [0219. 存在重复元素II Contains Duplicate II](0219.contains-duplicate-ii/index.md)
-    - [0231. 2的幂 Power of Two](0231.power-of-two/index.md)
-    - [0326. 3的幂 Power of Three](0326.power-of-three/index.md)
-    - [0338. 比特位计数 Counting Bits](0338.counting-bits/index.md)
-    - [0342. 4的幂 Power of Four](0342.power-of-four/index.md)
-    - [1518. 换水问题 Water Bottles](1518.water-bottles/index.md)
-    - [1780. 判断一个数字是否可以表示成三的幂的和 Check if Number is a Sum of Powers of Three](1780.check-if-number-is-a-sum-of-powers-of-three/index.md)
-    - [2119. 反转两次的数字 A Number After a Double Reversal](2119.a-number-after-a-double-reversal/index.md)
\ No newline at end of file
diff --git a/src/leetcode/tags/math.md b/src/leetcode/tags/math.md
deleted file mode 100644
index 0157fb5e..00000000
--- a/src/leetcode/tags/math.md
+++ /dev/null
@@ -1,13 +0,0 @@
-# 数学问题的问题列表
-
-## 简单
-
-- [2119. 反转两次的数字 A Number After a Double Reversal](../leetcode/2119.a-number-after-a-double-reversal/index.md)
-- [1518. 换水问题 Water Bottles](../leetcode/1518.water-bottles/index.md)
-
-## 中等
-
-- [0007. 整数反转 Reverse Integer](../leetcode/0007.reverse-integer/index.md)
-- [1780. 判断一个数字是否可以表示成三的幂的和 Check if Number is a Sum of Powers of Three](../leetcode/1780.check-if-number-is-a-sum-of-powers-of-three/index.md)
-
-- [3100. Water Bottles II](https://leetcode.com/problems/water-bottles-ii)
\ No newline at end of file
diff --git a/src/strings/index.md b/src/string/index.md
similarity index 100%
rename from src/strings/index.md
rename to src/string/index.md
diff --git a/src/strings/problems.md b/src/string/problems.md
similarity index 100%
rename from src/strings/problems.md
rename to src/string/problems.md