// IMPORTANT: Please reset any member data you declared, as

// the same Solution instance will be reused for each test case.

int* array = new int[n];

array[0] = 1;

for(int i = 1; i < n; i ++){

array[i] = numTrees(i);

}

int ret = 0;

for(int i = 0; i < n; i++){

ret += array[i] * array[n-i-1];

}

return ret;