具体思路:
DP或者递归都行;
具体代码:
class Solution {
public:
int numTrees(int n) {
if(n<1)
return 1;
if(n==2)
return 2;
int sum=0;
for(int i=1;i<=n;i++){
sum+=numTrees(i-1)*numTrees(n-i);
}
return sum;
}
};