feat: add cs solution to lc problem: No.1424 (doocs#1998)

Author: dev-mauli

solution/1400-1499/1424.Diagonal Traverse II/README.md

@@ -151,6 +151,27 @@ func findDiagonalOrder(nums [][]int) []int {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] FindDiagonalOrder(IList<IList<int>> nums) {
+        List<int[]> arr = new List<int[]>();
+        for (int i = 0; i < nums.Count; ++i) {
+            for (int j = 0; j < nums[i].Count; ++j) {
+                arr.Add(new int[] { i + j, j, nums[i][j] });
+            }
+        }
+        arr.Sort((a, b) => a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]);
+        int[] ans = new int[arr.Count];
+        for (int i = 0; i < arr.Count; ++i) {
+            ans[i] = arr[i][2];
+        }
+        return ans;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1400-1499/1424.Diagonal Traverse II/README_EN.md

@@ -115,6 +115,27 @@ func findDiagonalOrder(nums [][]int) []int {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] FindDiagonalOrder(IList<IList<int>> nums) {
+        List<int[]> arr = new List<int[]>();
+        for (int i = 0; i < nums.Count; ++i) {
+            for (int j = 0; j < nums[i].Count; ++j) {
+                arr.Add(new int[] { i + j, j, nums[i][j] });
+            }
+        }
+        arr.Sort((a, b) => a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]);
+        int[] ans = new int[arr.Count];
+        for (int i = 0; i < arr.Count; ++i) {
+            ans[i] = arr[i][2];
+        }
+        return ans;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1400-1499/1424.Diagonal Traverse II/Solution.cs

@@ -0,0 +1,16 @@
+public class Solution {
+    public int[] FindDiagonalOrder(IList<IList<int>> nums) {
+        List<int[]> arr = new List<int[]>();
+        for (int i = 0; i < nums.Count; ++i) {
+            for (int j = 0; j < nums[i].Count; ++j) {
+                arr.Add(new int[] { i + j, j, nums[i][j] });
+            }
+        }
+        arr.Sort((a, b) => a[0] == b[0] ? a[1] - b[1] : a[0] - b[0]);
+        int[] ans = new int[arr.Count];
+        for (int i = 0; i < arr.Count; ++i) {
+            ans[i] = arr[i][2];
+        }
+        return ans;
+    }
+}