feat: update solutions to lc problems: No.1171,1891 (#1843)

* No.1171.Remove Zero Sum Consecutive Nodes from Linked List
* No.1891.Cutting Ribbons

Author: yanglbme

solution/1100-1199/1171.Remove Zero Sum Consecutive Nodes from Linked List/README.md

@@ -229,7 +229,7 @@ function removeZeroSumSublists(head: ListNode | null): ListNode | null {
 
 ### **Rust**
 
-```
+```rust
 // Definition for singly-linked list.
 // #[derive(PartialEq, Eq, Clone, Debug)]
 // pub struct ListNode {

solution/1100-1199/1171.Remove Zero Sum Consecutive Nodes from Linked List/README_EN.md

@@ -43,6 +43,18 @@
 
 ## Solutions
 
+**Solution 1: Prefix Sum + Hash Table**
+
+If two prefix sums of the linked list are equal, it means that the sum of the continuous node sequence between the two prefix sums is $0$, so we can remove this part of the continuous nodes.
+
+We first traverse the linked list and use a hash table $last$ to record the prefix sum and the corresponding linked list node. For the same prefix sum $s$, the later node overwrites the previous node.
+
+Next, we traverse the linked list again. If the current node $cur$ has a prefix sum $s$ that appears in $last$, it means that the sum of all nodes between $cur$ and $last[s]$ is $0$, so we directly modify the pointer of $cur$ to $last[s].next$, which removes this part of the continuous nodes with a sum of $0$. We continue to traverse and delete all continuous nodes with a sum of $0$.
+
+Finally, we return the head node of the linked list $dummy.next$.
+
+The time complexity is $O(n)$, and the space complexity is $O(n)$. Here, $n$ is the length of the linked list.
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -208,7 +220,7 @@ function removeZeroSumSublists(head: ListNode | null): ListNode | null {
 
 ### **Rust**
 
-```
+```rust
 // Definition for singly-linked list.
 // #[derive(PartialEq, Eq, Clone, Debug)]
 // pub struct ListNode {

solution/1800-1899/1891.Cutting Ribbons/README.md

@@ -74,7 +74,7 @@
 
 最后，我们返回 $left$ 即可。
 
-时间复杂度 $O(n \times \log M)$，空间复杂度 $O(1)$。其中 $n$ 和 $M$ 分别为绳子的数量和绳子的最大长度。
+时间复杂度 $O(n \times \log M)$，其中 $n$ 和 $M$ 分别为绳子的数量和绳子的最大长度。空间复杂度 $O(1)$。
 
 <!-- tabs:start -->
 
@@ -232,7 +232,7 @@ function maxLength(ribbons: number[], k: number): number {
 
 ```rust
 impl Solution {
-    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+    pub fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
         let mut left = 0i32;
         let mut right = *ribbons.iter().max().unwrap();
         while left < right {

solution/1800-1899/1891.Cutting Ribbons/README_EN.md

@@ -65,6 +65,16 @@ Now you have 4 ribbons of length 4.
 
 ## Solutions
 
+**Solution 1: Binary Search**
+
+We observe that if we can obtain $k$ ropes of length $x$, then we can also obtain $k$ ropes of length $x-1$. This implies that there is a monotonicity property, and we can use binary search to find the maximum length $x$ such that we can obtain $k$ ropes of length $x$.
+
+We define the left boundary of the binary search as $left=0$, the right boundary as $right=\max(ribbons)$, and the middle value as $mid=(left+right+1)/2$. We then calculate the number of ropes we can obtain with length $mid$, denoted as $cnt$. If $cnt \geq k$, it means we can obtain $k$ ropes of length $mid$, so we update $left$ to $mid$. Otherwise, we update $right$ to $mid-1$.
+
+Finally, we return $left$ as the maximum length of the ropes we can obtain.
+
+The time complexity is $O(n \times \log M)$, where $n$ and $M$ are the number of ropes and the maximum length of the ropes, respectively. The space complexity is $O(1)$.
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -217,7 +227,7 @@ function maxLength(ribbons: number[], k: number): number {
 
 ```rust
 impl Solution {
-    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+    pub fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
         let mut left = 0i32;
         let mut right = *ribbons.iter().max().unwrap();
         while left < right {

solution/1800-1899/1891.Cutting Ribbons/Solution.rs

@@ -1,5 +1,5 @@
 impl Solution {
-    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+    pub fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
         let mut left = 0i32;
         let mut right = *ribbons.iter().max().unwrap();
         while left < right {