feat: add rust solution to lc problem: No.1891 (#1833)

No.1891.Cutting Ribbons

Author: methanoya

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

@@ -228,6 +228,33 @@ function maxLength(ribbons: number[], k: number): number {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+        let mut left = 0i32;
+        let mut right = *ribbons.iter().max().unwrap();
+        while left < right {
+            let mid = (left + right + 1) / 2;
+            let mut cnt = 0i32;
+            for &entry in ribbons.iter() {
+                cnt += entry / mid;
+                if cnt >= k {
+                    break;
+                }
+            }
+            if cnt >= k {
+                left = mid;
+            } else {
+                right = mid - 1;
+            }
+        }
+        return left;
+    }
+}
+```
+
 ### **...**
 
 ```

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

@@ -213,6 +213,33 @@ function maxLength(ribbons: number[], k: number): number {
 }
 ```
 
+### **Rust**
+
+```rust
+impl Solution {
+    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+        let mut left = 0i32;
+        let mut right = *ribbons.iter().max().unwrap();
+        while left < right {
+            let mid = (left + right + 1) / 2;
+            let mut cnt = 0i32;
+            for &entry in ribbons.iter() {
+                cnt += entry / mid;
+                if cnt >= k {
+                    break;
+                }
+            }
+            if cnt >= k {
+                left = mid;
+            } else {
+                right = mid - 1;
+            }
+        }
+        return left;
+    }
+}
+```
+
 ### **...**
 
 ```

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

@@ -0,0 +1,22 @@
+impl Solution {
+    fn max_length(ribbons: Vec<i32>, k: i32) -> i32 {
+        let mut left = 0i32;
+        let mut right = *ribbons.iter().max().unwrap();
+        while left < right {
+            let mid = (left + right + 1) / 2;
+            let mut cnt = 0i32;
+            for &entry in ribbons.iter() {
+                cnt += entry / mid;
+                if cnt >= k {
+                    break;
+                }
+            }
+            if cnt >= k {
+                left = mid;
+            } else {
+                right = mid - 1;
+            }
+        }
+        return left;
+    }
+}