diff --git a/README.md b/README.md
index 09eb094bc..55bf53546 100644
--- a/README.md
+++ b/README.md
@@ -62,14 +62,15 @@ LeetCode Problems' Solutions
| # | Title | Solution | Difficulty |
| :-: | - | - | :-: |
+| 1279 | [Traffic Light Controlled Intersection](https://leetcode.com/problems/traffic-light-controlled-intersection) 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/traffic-light-controlled-intersection) | Easy |
| 1278 | [Palindrome Partitioning III](https://leetcode.com/problems/palindrome-partitioning-iii "分割回文串 III") | [Go](https://github.com/openset/leetcode/tree/master/problems/palindrome-partitioning-iii) | Hard |
| 1277 | [Count Square Submatrices with All Ones](https://leetcode.com/problems/count-square-submatrices-with-all-ones "统计全为 1 的正方形子矩阵") | [Go](https://github.com/openset/leetcode/tree/master/problems/count-square-submatrices-with-all-ones) | Medium |
| 1276 | [Number of Burgers with No Waste of Ingredients](https://leetcode.com/problems/number-of-burgers-with-no-waste-of-ingredients "不浪费原料的汉堡制作方案") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-burgers-with-no-waste-of-ingredients) | Medium |
| 1275 | [Find Winner on a Tic Tac Toe Game](https://leetcode.com/problems/find-winner-on-a-tic-tac-toe-game "找出井字棋的获胜者") | [Go](https://github.com/openset/leetcode/tree/master/problems/find-winner-on-a-tic-tac-toe-game) | Easy |
-| 1274 | [Number of Ships in a Rectangle](https://leetcode.com/problems/number-of-ships-in-a-rectangle "矩形内船只的数目") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-ships-in-a-rectangle) | Hard |
-| 1273 | [Delete Tree Nodes](https://leetcode.com/problems/delete-tree-nodes "删除树节点") | [Go](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) | Medium |
-| 1272 | [Remove Interval](https://leetcode.com/problems/remove-interval "删除区间") | [Go](https://github.com/openset/leetcode/tree/master/problems/remove-interval) | Medium |
-| 1271 | [Hexspeak](https://leetcode.com/problems/hexspeak "十六进制魔术数字") | [Go](https://github.com/openset/leetcode/tree/master/problems/hexspeak) | Easy |
+| 1274 | [Number of Ships in a Rectangle](https://leetcode.com/problems/number-of-ships-in-a-rectangle "矩形内船只的数目") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-ships-in-a-rectangle) | Hard |
+| 1273 | [Delete Tree Nodes](https://leetcode.com/problems/delete-tree-nodes "删除树节点") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) | Medium |
+| 1272 | [Remove Interval](https://leetcode.com/problems/remove-interval "删除区间") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/remove-interval) | Medium |
+| 1271 | [Hexspeak](https://leetcode.com/problems/hexspeak "十六进制魔术数字") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/hexspeak) | Easy |
| 1270 | [All People Report to the Given Manager](https://leetcode.com/problems/all-people-report-to-the-given-manager) 🔒 | [MySQL](https://github.com/openset/leetcode/tree/master/problems/all-people-report-to-the-given-manager) | Medium |
| 1269 | [Number of Ways to Stay in the Same Place After Some Steps](https://leetcode.com/problems/number-of-ways-to-stay-in-the-same-place-after-some-steps "停在原地的方案数") | [Go](https://github.com/openset/leetcode/tree/master/problems/number-of-ways-to-stay-in-the-same-place-after-some-steps) | Hard |
| 1268 | [Search Suggestions System](https://leetcode.com/problems/search-suggestions-system "搜索推荐系统") | [Go](https://github.com/openset/leetcode/tree/master/problems/search-suggestions-system) | Medium |
diff --git a/problems/minimum-moves-to-move-a-box-to-their-target-location/README.md b/problems/minimum-moves-to-move-a-box-to-their-target-location/README.md
index d88a98af3..9aedc534b 100644
--- a/problems/minimum-moves-to-move-a-box-to-their-target-location/README.md
+++ b/problems/minimum-moves-to-move-a-box-to-their-target-location/README.md
@@ -13,7 +13,7 @@
Storekeeper is a game in which the player pushes boxes around in a warehouse trying to get them to target locations.
-The game is represented by a grid of size n*m, where each element is a wall, floor, or a box.
+The game is represented by a grid of size m x n, where each element is a wall, floor, or a box.
Your task is move the box 'B' to the target position 'T' under the following rules:
@@ -81,8 +81,10 @@
Constraints:
- 1 <= grid.length <= 201 <= grid[i].length <= 20m == grid.lengthn == grid[i].length1 <= m <= 201 <= n <= 20grid contains only characters '.', '#', 'S' , 'T', or 'B'.- There is only one character
'S', 'B' and 'T' in the grid.
diff --git a/problems/palindrome-partitioning-iii/README.md b/problems/palindrome-partitioning-iii/README.md
index 2a6f6908c..756123c04 100644
--- a/problems/palindrome-partitioning-iii/README.md
+++ b/problems/palindrome-partitioning-iii/README.md
@@ -7,7 +7,7 @@
[< Previous](https://github.com/openset/leetcode/tree/master/problems/count-square-submatrices-with-all-ones "Count Square Submatrices with All Ones")
-Next >
+[Next >](https://github.com/openset/leetcode/tree/master/problems/traffic-light-controlled-intersection "Traffic Light Controlled Intersection")
## [1278. Palindrome Partitioning III (Hard)](https://leetcode.com/problems/palindrome-partitioning-iii "分割回文串 III")
diff --git a/problems/populating-next-right-pointers-in-each-node-ii/README.md b/problems/populating-next-right-pointers-in-each-node-ii/README.md
index 0bf62d507..4f3ba254b 100644
--- a/problems/populating-next-right-pointers-in-each-node-ii/README.md
+++ b/problems/populating-next-right-pointers-in-each-node-ii/README.md
@@ -28,25 +28,30 @@ struct Node {
-Example:
+Follow up:
-
+
+ - You may only use constant extra space.
+ - Recursive approach is fine, you may assume implicit stack space does not count as extra space for this problem.
+
-
-Input: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":null,"next":null,"right":{"$id":"6","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}
+
+Example 1:
-Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":null,"right":null,"val":7},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"6","left":null,"next":null,"right":{"$ref":"5"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"6"},"val":1}
+
-Explanation: Given the above binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.
+
+Input: root = [1,2,3,4,5,null,7]
+Output: [1,#,2,3,#,4,5,7,#]
+Explanation: Given the above binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B. The serialized output is in level order as connected by the next pointers, with '#' signifying the end of each level.
-
-Note:
+Constraints:
- - You may only use constant extra space.
- - Recursive approach is fine, implicit stack space does not count as extra space for this problem.
+ - The number of nodes in the given tree is less than
6000.
+ -100 <= node.val <= 100
### Related Topics
diff --git a/problems/populating-next-right-pointers-in-each-node/README.md b/problems/populating-next-right-pointers-in-each-node/README.md
index 78591ccd9..3609677d7 100644
--- a/problems/populating-next-right-pointers-in-each-node/README.md
+++ b/problems/populating-next-right-pointers-in-each-node/README.md
@@ -28,25 +28,30 @@ struct Node {
-Example:
+Follow up:
-
+
+ - You may only use constant extra space.
+ - Recursive approach is fine, you may assume implicit stack space does not count as extra space for this problem.
+
-
-Input: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}
+
+Example 1:
-Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1}
+
-Explanation: Given the above perfect binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.
+
+Input: root = [1,2,3,4,5,6,7]
+Output: [1,#,2,3,#,4,5,6,7,#]
+Explanation: Given the above perfect binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B. The serialized output is in level order as connected by the next pointers, with '#' signifying the end of each level.
-
-Note:
+Constraints:
- - You may only use constant extra space.
- - Recursive approach is fine, implicit stack space does not count as extra space for this problem.
+ - The number of nodes in the given tree is less than
4096.
+ -1000 <= node.val <= 1000
### Related Topics
diff --git a/problems/reach-a-number/README.md b/problems/reach-a-number/README.md
index b13e05bc4..52f48248a 100644
--- a/problems/reach-a-number/README.md
+++ b/problems/reach-a-number/README.md
@@ -9,7 +9,7 @@
[Next >](https://github.com/openset/leetcode/tree/master/problems/pour-water "Pour Water")
-## [754. Reach a Number (Easy)](https://leetcode.com/problems/reach-a-number "到达终点数字")
+## [754. Reach a Number (Medium)](https://leetcode.com/problems/reach-a-number "到达终点数字")
You are standing at position 0 on an infinite number line. There is a goal at position target.
diff --git a/problems/search-suggestions-system/README.md b/problems/search-suggestions-system/README.md
index ccc592bc4..75f7f25a8 100644
--- a/problems/search-suggestions-system/README.md
+++ b/problems/search-suggestions-system/README.md
@@ -58,6 +58,7 @@ After typing mou, mous and mouse the system suggests ["mouse","mo
1 <= products.length <= 1000- There are no repeated elements in
products.
1 <= Σ products[i].length <= 2 * 10^4- All characters of
products[i] are lower-case English letters.
1 <= searchWord.length <= 1000Given a 2D grid of size n * m and an integer k. You need to shift the grid k times.
+Given a 2D grid of size m x n and an integer k. You need to shift the grid k times.
In one shift operation:
- Element at
grid[i][j] becomes at grid[i][j + 1].
- - Element at
grid[i][m - 1] becomes at grid[i + 1][0].
- - Element at
grid[n - 1][m - 1] becomes at grid[0][0].
+ - Element at
grid[i][n - 1] becomes at grid[i + 1][0].
+ - Element at
grid[n - 1][n - 1] becomes at grid[0][0].
Return the 2D grid after applying shift operation k times.
@@ -49,8 +49,10 @@
Constraints:
- 1 <= grid.length <= 501 <= grid[i].length <= 50m == grid.lengthn == grid[i].length1 <= m <= 501 <= n <= 50-1000 <= grid[i][j] <= 10000 <= k <= 100
diff --git a/problems/similar-string-groups/README.md b/problems/similar-string-groups/README.md
index 26d131081..485e93fcd 100644
--- a/problems/similar-string-groups/README.md
+++ b/problems/similar-string-groups/README.md
@@ -19,22 +19,22 @@
We are given a list A of strings. Every string in A is an anagram of every other string in A. How many groups are there?
+
Example 1:
-
-
-Input: ["tars","rats","arts","star"]
-Output: 2
-
-Note:
-
-
- A.length <= 2000A[i].length <= 1000Input: A = ["tars","rats","arts","star"]
+Output: 2
+
+
+Constraints:
+
+
+ 1 <= A.length <= 20001 <= A[i].length <= 1000A.length * A[i].length <= 20000- All words in
A consist of lowercase letters only.
- All words in
A have the same length and are anagrams of each other.
- The judging time limit has been increased for this question.
-
+
### Related Topics
[[Depth-first Search](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)]
diff --git a/problems/traffic-light-controlled-intersection/README.md b/problems/traffic-light-controlled-intersection/README.md
new file mode 100644
index 000000000..abc12d6ff
--- /dev/null
+++ b/problems/traffic-light-controlled-intersection/README.md
@@ -0,0 +1,14 @@
+
+
+
+
+
+
+
+[< Previous](https://github.com/openset/leetcode/tree/master/problems/palindrome-partitioning-iii "Palindrome Partitioning III")
+
+Next >
+
+## [1279. Traffic Light Controlled Intersection (Easy)](https://leetcode.com/problems/traffic-light-controlled-intersection "")
+
+
diff --git a/readme/601-900.md b/readme/601-900.md
index 9d56d44d4..acfd38646 100644
--- a/readme/601-900.md
+++ b/readme/601-900.md
@@ -215,7 +215,7 @@ LeetCode Problems' Solutions
| 751 | [IP to CIDR](https://leetcode.com/problems/ip-to-cidr "IP 到 CIDR") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/ip-to-cidr) | Easy |
| 752 | [Open the Lock](https://leetcode.com/problems/open-the-lock "打开转盘锁") | [Go](https://github.com/openset/leetcode/tree/master/problems/open-the-lock) | Medium |
| 753 | [Cracking the Safe](https://leetcode.com/problems/cracking-the-safe "破解保险箱") | [Go](https://github.com/openset/leetcode/tree/master/problems/cracking-the-safe) | Hard |
-| 754 | [Reach a Number](https://leetcode.com/problems/reach-a-number "到达终点数字") | [Go](https://github.com/openset/leetcode/tree/master/problems/reach-a-number) | Easy |
+| 754 | [Reach a Number](https://leetcode.com/problems/reach-a-number "到达终点数字") | [Go](https://github.com/openset/leetcode/tree/master/problems/reach-a-number) | Medium |
| 755 | [Pour Water](https://leetcode.com/problems/pour-water "倒水") 🔒 | [Go](https://github.com/openset/leetcode/tree/master/problems/pour-water) | Medium |
| 756 | [Pyramid Transition Matrix](https://leetcode.com/problems/pyramid-transition-matrix "金字塔转换矩阵") | [Go](https://github.com/openset/leetcode/tree/master/problems/pyramid-transition-matrix) | Medium |
| 757 | [Set Intersection Size At Least Two](https://leetcode.com/problems/set-intersection-size-at-least-two " 设置交集大小至少为2") | [Go](https://github.com/openset/leetcode/tree/master/problems/set-intersection-size-at-least-two) | Hard |
diff --git a/tag/depth-first-search/README.md b/tag/depth-first-search/README.md
index 287f56c0b..c2ea6715c 100644
--- a/tag/depth-first-search/README.md
+++ b/tag/depth-first-search/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 1273 | [删除树节点](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
+| 1273 | [删除树节点](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) 🔒 | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
| 1254 | [统计封闭岛屿的数目](https://github.com/openset/leetcode/tree/master/problems/number-of-closed-islands) | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] | Medium |
| 1245 | [树的直径](https://github.com/openset/leetcode/tree/master/problems/tree-diameter) 🔒 | [[树](https://github.com/openset/leetcode/tree/master/tag/tree/README.md)] [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[广度优先搜索](https://github.com/openset/leetcode/tree/master/tag/breadth-first-search/README.md)] | Medium |
| 1242 | [多线程网页爬虫](https://github.com/openset/leetcode/tree/master/problems/web-crawler-multithreaded) 🔒 | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[广度优先搜索](https://github.com/openset/leetcode/tree/master/tag/breadth-first-search/README.md)] | Medium |
diff --git a/tag/divide-and-conquer/README.md b/tag/divide-and-conquer/README.md
index 43fa7f252..aee63daf9 100644
--- a/tag/divide-and-conquer/README.md
+++ b/tag/divide-and-conquer/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 1274 | [矩形内船只的数目](https://github.com/openset/leetcode/tree/master/problems/number-of-ships-in-a-rectangle) | [[分治算法](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)] | Hard |
+| 1274 | [矩形内船只的数目](https://github.com/openset/leetcode/tree/master/problems/number-of-ships-in-a-rectangle) 🔒 | [[分治算法](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)] | Hard |
| 973 | [最接近原点的 K 个点](https://github.com/openset/leetcode/tree/master/problems/k-closest-points-to-origin) | [[堆](https://github.com/openset/leetcode/tree/master/tag/heap/README.md)] [[排序](https://github.com/openset/leetcode/tree/master/tag/sort/README.md)] [[分治算法](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)] | Medium |
| 932 | [漂亮数组](https://github.com/openset/leetcode/tree/master/problems/beautiful-array) | [[分治算法](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)] | Medium |
| 903 | [DI 序列的有效排列](https://github.com/openset/leetcode/tree/master/problems/valid-permutations-for-di-sequence) | [[分治算法](https://github.com/openset/leetcode/tree/master/tag/divide-and-conquer/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
diff --git a/tag/dynamic-programming/README.md b/tag/dynamic-programming/README.md
index 80acb8862..dffff9f47 100644
--- a/tag/dynamic-programming/README.md
+++ b/tag/dynamic-programming/README.md
@@ -11,7 +11,7 @@
| :-: | - | - | :-: |
| 1278 | [分割回文串 III](https://github.com/openset/leetcode/tree/master/problems/palindrome-partitioning-iii) | [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
| 1277 | [统计全为 1 的正方形子矩阵](https://github.com/openset/leetcode/tree/master/problems/count-square-submatrices-with-all-ones) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
-| 1273 | [删除树节点](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
+| 1273 | [删除树节点](https://github.com/openset/leetcode/tree/master/problems/delete-tree-nodes) 🔒 | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
| 1269 | [停在原地的方案数](https://github.com/openset/leetcode/tree/master/problems/number-of-ways-to-stay-in-the-same-place-after-some-steps) | [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
| 1262 | [可被三整除的最大和](https://github.com/openset/leetcode/tree/master/problems/greatest-sum-divisible-by-three) | [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Medium |
| 1259 | [不相交的握手](https://github.com/openset/leetcode/tree/master/problems/handshakes-that-dont-cross) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
diff --git a/tag/line-sweep/README.md b/tag/line-sweep/README.md
index 7ff93a834..750a31aab 100644
--- a/tag/line-sweep/README.md
+++ b/tag/line-sweep/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 1272 | [删除区间](https://github.com/openset/leetcode/tree/master/problems/remove-interval) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Medium |
+| 1272 | [删除区间](https://github.com/openset/leetcode/tree/master/problems/remove-interval) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Medium |
| 1229 | [安排会议日程](https://github.com/openset/leetcode/tree/master/problems/meeting-scheduler) 🔒 | [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Medium |
| 850 | [矩形面积 II](https://github.com/openset/leetcode/tree/master/problems/rectangle-area-ii) | [[线段树](https://github.com/openset/leetcode/tree/master/tag/segment-tree/README.md)] [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Hard |
| 391 | [完美矩形](https://github.com/openset/leetcode/tree/master/problems/perfect-rectangle) | [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Hard |
diff --git a/tag/math/README.md b/tag/math/README.md
index 7f04342fd..0add6e3e2 100644
--- a/tag/math/README.md
+++ b/tag/math/README.md
@@ -10,8 +10,8 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
| 1276 | [不浪费原料的汉堡制作方案](https://github.com/openset/leetcode/tree/master/problems/number-of-burgers-with-no-waste-of-ingredients) | [[贪心算法](https://github.com/openset/leetcode/tree/master/tag/greedy/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
-| 1272 | [删除区间](https://github.com/openset/leetcode/tree/master/problems/remove-interval) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Medium |
-| 1271 | [十六进制魔术数字](https://github.com/openset/leetcode/tree/master/problems/hexspeak) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
+| 1272 | [删除区间](https://github.com/openset/leetcode/tree/master/problems/remove-interval) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[Line Sweep](https://github.com/openset/leetcode/tree/master/tag/line-sweep/README.md)] | Medium |
+| 1271 | [十六进制魔术数字](https://github.com/openset/leetcode/tree/master/problems/hexspeak) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1259 | [不相交的握手](https://github.com/openset/leetcode/tree/master/problems/handshakes-that-dont-cross) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[动态规划](https://github.com/openset/leetcode/tree/master/tag/dynamic-programming/README.md)] | Hard |
| 1256 | [加密数字](https://github.com/openset/leetcode/tree/master/problems/encode-number) 🔒 | [[位运算](https://github.com/openset/leetcode/tree/master/tag/bit-manipulation/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
| 1253 | [重构 2 行二进制矩阵](https://github.com/openset/leetcode/tree/master/problems/reconstruct-a-2-row-binary-matrix) | [[贪心算法](https://github.com/openset/leetcode/tree/master/tag/greedy/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
@@ -90,7 +90,7 @@
| 781 | [森林中的兔子](https://github.com/openset/leetcode/tree/master/problems/rabbits-in-forest) | [[哈希表](https://github.com/openset/leetcode/tree/master/tag/hash-table/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
| 780 | [到达终点](https://github.com/openset/leetcode/tree/master/problems/reaching-points) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Hard |
| 775 | [全局倒置与局部倒置](https://github.com/openset/leetcode/tree/master/problems/global-and-local-inversions) | [[数组](https://github.com/openset/leetcode/tree/master/tag/array/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
-| 754 | [到达终点数字](https://github.com/openset/leetcode/tree/master/problems/reach-a-number) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Easy |
+| 754 | [到达终点数字](https://github.com/openset/leetcode/tree/master/problems/reach-a-number) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
| 753 | [破解保险箱](https://github.com/openset/leetcode/tree/master/problems/cracking-the-safe) | [[深度优先搜索](https://github.com/openset/leetcode/tree/master/tag/depth-first-search/README.md)] [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Hard |
| 728 | [自除数](https://github.com/openset/leetcode/tree/master/problems/self-dividing-numbers) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Easy |
| 672 | [灯泡开关 Ⅱ](https://github.com/openset/leetcode/tree/master/problems/bulb-switcher-ii) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] | Medium |
diff --git a/tag/string/README.md b/tag/string/README.md
index c87d3c819..3db7038fb 100644
--- a/tag/string/README.md
+++ b/tag/string/README.md
@@ -9,7 +9,7 @@
| # | 题名 | 标签 | 难度 |
| :-: | - | - | :-: |
-| 1271 | [十六进制魔术数字](https://github.com/openset/leetcode/tree/master/problems/hexspeak) | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
+| 1271 | [十六进制魔术数字](https://github.com/openset/leetcode/tree/master/problems/hexspeak) 🔒 | [[数学](https://github.com/openset/leetcode/tree/master/tag/math/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Easy |
| 1268 | [搜索推荐系统](https://github.com/openset/leetcode/tree/master/problems/search-suggestions-system) | [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
| 1249 | [移除无效的括号](https://github.com/openset/leetcode/tree/master/problems/minimum-remove-to-make-valid-parentheses) | [[栈](https://github.com/openset/leetcode/tree/master/tag/stack/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |
| 1247 | [交换字符使得字符串相同](https://github.com/openset/leetcode/tree/master/problems/minimum-swaps-to-make-strings-equal) | [[贪心算法](https://github.com/openset/leetcode/tree/master/tag/greedy/README.md)] [[字符串](https://github.com/openset/leetcode/tree/master/tag/string/README.md)] | Medium |