feat: add solutions to lc problem: No.2221 (#4758)

Author: yanglbme

solution/2200-2299/2221.Find Triangular Sum of an Array/README.md

@@ -145,6 +145,38 @@ function triangularSum(nums: number[]): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn triangular_sum(mut nums: Vec<i32>) -> i32 {
+        let mut k = nums.len() as i32 - 1;
+        while k > 0 {
+            for i in 0..k as usize {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+            k -= 1;
+        }
+        nums[0]
+    }
+}
+```
+
+#### C#
+
+```cs
+public class Solution {
+    public int TriangularSum(int[] nums) {
+        for (int k = nums.Length - 1; k > 0; --k) {
+            for (int i = 0; i < k; ++i) {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+        }
+        return nums[0];
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/2200-2299/2221.Find Triangular Sum of an Array/README_EN.md

@@ -141,6 +141,38 @@ function triangularSum(nums: number[]): number {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn triangular_sum(mut nums: Vec<i32>) -> i32 {
+        let mut k = nums.len() as i32 - 1;
+        while k > 0 {
+            for i in 0..k as usize {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+            k -= 1;
+        }
+        nums[0]
+    }
+}
+```
+
+#### C#
+
+```cs
+public class Solution {
+    public int TriangularSum(int[] nums) {
+        for (int k = nums.Length - 1; k > 0; --k) {
+            for (int i = 0; i < k; ++i) {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+        }
+        return nums[0];
+    }
+}
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/2200-2299/2221.Find Triangular Sum of an Array/Solution.cs

@@ -0,0 +1,10 @@
+public class Solution {
+    public int TriangularSum(int[] nums) {
+        for (int k = nums.Length - 1; k > 0; --k) {
+            for (int i = 0; i < k; ++i) {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+        }
+        return nums[0];
+    }
+}

solution/2200-2299/2221.Find Triangular Sum of an Array/Solution.rs

@@ -0,0 +1,12 @@
+impl Solution {
+    pub fn triangular_sum(mut nums: Vec<i32>) -> i32 {
+        let mut k = nums.len() as i32 - 1;
+        while k > 0 {
+            for i in 0..k as usize {
+                nums[i] = (nums[i] + nums[i + 1]) % 10;
+            }
+            k -= 1;
+        }
+        nums[0]
+    }
+}