Description
Given n, how many structurally unique BST's (binary search trees) that store values 1...n?
Example
Given n = 3, there are a total of 5 unique BST's.
1 3 3 2 1
/ / /
3 2 1 1 3 2
/ /
2 1 2 3思路
- 动态规划。
- 其实也就是看用这么多相同节点能构造多少个这种结构
代码
class Solution {
public:
int numTrees(int n) {
if(n <= 2) return n;
vector<int> dp(n + 1, 0);
dp[0] = 1;
dp[1] = 1;
dp[2] = 2;
for(int i = 3; i <= n; ++i){
for(int j = 0; j < i; ++j)
dp[i] += dp[j] * dp[i - j - 1];
}
return dp[n];
}
};内容来源于网络如有侵权请私信删除
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