[leetcode] Unique Binary Search Trees

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