Create pairing.java

pairing.java

@@ -0,0 +1,29 @@
+import java.io.*;
+
+class GFG {
+
+    // Returns count of ways n people
+    // can remain single or paired up.
+    static int countFriendsPairings(int n)
+    {
+        int dp[] = new int[n + 1];
+
+        // Filling dp[] in bottom-up manner using
+        // recursive formula explained above.
+        for (int i = 0; i <= n; i++) {
+            if (i <= 2)
+                dp[i] = i;
+            else
+                dp[i] = dp[i - 1] + (i - 1) * dp[i - 2];
+        }
+
+        return dp[n];
+    }
+
+    // Driver code
+    public static void main(String[] args)
+    {
+        int n = 4;
+        System.out.println(countFriendsPairings(n));
+    }
+}