Unique Binary Search Trees

使用带标记的DP

        int result[1000];int numTrees(int n) {result[0] = 1;result[1] = 1;result[2] = 2;// Start typing your C/C++ solution below// DO NOT write int main() functionif(result[n] != 0)return result[n];int num = 0, t;for(t = 1; t <= n; t++){num = num + numTrees(t-1)*numTrees(n-t);}return num;}