feat: add cs solution to lc problem: No.1921 (#1939)

Author: dev-mauli

solution/1900-1999/1921.Eliminate Maximum Number of Monsters/README.md

@@ -202,6 +202,27 @@ var eliminateMaximum = function (dist, speed) {
 };
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int EliminateMaximum(int[] dist, int[] speed) {
+        int n = dist.Length;
+        int[] times = new int[n];
+        for (int i = 0; i < n; ++i) {
+            times[i] = (dist[i] - 1) / speed[i];
+        }
+        Array.Sort(times);
+        for (int i = 0; i < n; ++i) {
+            if (times[i] < i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1900-1999/1921.Eliminate Maximum Number of Monsters/README_EN.md

@@ -177,6 +177,27 @@ var eliminateMaximum = function (dist, speed) {
 };
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int EliminateMaximum(int[] dist, int[] speed) {
+        int n = dist.Length;
+        int[] times = new int[n];
+        for (int i = 0; i < n; ++i) {
+            times[i] = (dist[i] - 1) / speed[i];
+        }
+        Array.Sort(times);
+        for (int i = 0; i < n; ++i) {
+            if (times[i] < i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/1900-1999/1921.Eliminate Maximum Number of Monsters/Solution.cs

@@ -0,0 +1,16 @@
+public class Solution {
+    public int EliminateMaximum(int[] dist, int[] speed) {
+        int n = dist.Length;
+        int[] times = new int[n];
+        for (int i = 0; i < n; ++i) {
+            times[i] = (dist[i] - 1) / speed[i];
+        }
+        Array.Sort(times);
+        for (int i = 0; i < n; ++i) {
+            if (times[i] < i) {
+                return i;
+            }
+        }
+        return n;
+    }
+}