create 2002 in c#

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;
+ }
+}