10.3

Author: huangyt39

163.py

@@ -0,0 +1,24 @@
+class Solution:
+    """
+    @param n: An integer
+    @return: An integer
+    """
+    def numTrees(self, n):
+        # write your code here
+        if n == 0:
+            return 1
+        if n < 3:
+            return n
+        dp = [0] * (n+1)
+        dp[1] = 1
+        dp[2] = 2
+        for i in range(3, n+1):
+            
+            dp[i] = dp[i-1] * 2
+            for j in range(2, i):
+                dp[i] += (dp[j-1] * dp[i-j])
+        
+        return dp[n]
+                
+        
+