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Given n, how many structurally unique BST‘s (binary search trees) that store values 1...n?
For 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
class Solution {
public:
int numTrees(int n) {
vector<int> num;
num.push_back(1);
for(int i=1; i<=n; i++){
num.push_back(0);
if(i<3)
num[i]=i;
else{
for(int j=1; j<=i; j++)
num[i]+=num[j-1]*num[i-j];
}
}
return num[n];
}
};
leetcode：Unique Binary Search Trees
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原文地址：http://www.cnblogs.com/carsonzhu/p/4584538.html
