96(a).cpp

class Solution {
public:
    int numTrees(int n) {
        
        int dp[n+1];
        dp[0]=dp[1]=1;
        for(int i=2;i<=n;i++){
            dp[i]=0;
            for(int j=1;j<=i;j++){
                dp[i]+=dp[j-1]*dp[i-j];
            }
        }
        
        return dp[n];
        
    }
};