create 2002 in c#

Author: Mohammed785

csharp/2002-maximum-product-of-the-length of-2-palindromic-subsequences.cs

@@ -0,0 +1,50 @@
+public class Solution {
+    public int MaxProduct(string s) {
+        if(s == null || s.Length < 2)
+            return 0;
+        if(s.Length == 2)
+            return 1;
+
+        int n = s.Length;
+        int total = 1 << n;
+
+        List<(int, int)> possible = new List<(int, int)>();
+
+        for(int i = 0; i < total; i++) {
+            StringBuilder sb = new StringBuilder();
+
+            for(int j = 0; j < n; j++) {
+                if((i & (1 << j)) != 0) {
+                    sb.Append(s[j]);
+                }
+            }
+
+            if(IsPalindrome(sb.ToString())) {
+                possible.Add((i, sb.Length));
+            }
+        }
+
+        int ans = 0;
+        for(int i = 0; i < possible.Count; i++) {
+            int bitmask = possible[i].Item1;
+            int count = possible[i].Item2;
+            for(int j = i + 1; j < possible.Count; j++) {
+                int bitmask2 = possible[j].Item1;
+                int count2 = possible[j].Item2;
+                if((bitmask & bitmask2) == 0)
+                    ans = Math.Max(ans, count * count2);
+            }
+        }
+        return ans;
+    }
+
+    private bool IsPalindrome(string s){
+        int i = 0;
+        int j = s.Length - 1;
+        while(i < j) {
+            if(s[i++] != s[j--])
+                return false;
+        }
+        return true;
+    }
+}