[leetcode]96. Unique Binary Search Trees
Analysis
intern intern intern—— [每天刷题并不难0.0]
Given n, how many structurally unique BST’s (binary search trees) that store values 1 … n?
动态规划解决，状态转移方程：
DP[n] = DP[0]DP[n-1]+DP[1]DP[n-2]+…+DP[i-1]DP[n-i]+…DP[n-1]DP[0];
Implement
class Solution {
public:
int numTrees(int n) {
vector<int> DP(n+1, 0);
DP[0] = DP[1] = 1;
for(int i=2; i<=n; i++){
for(int j=1; j<=i; j++)
DP[i] += DP[j-1]*DP[i-j];
}
return DP[n];
}
};