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
给定一个数字n, 问用1,2,3,4,5...n这n个值，能构造多少棵合法的二叉搜索树
class Solution {
public:
int binaryTreeNums(int start, int end){
//[start, end]区间上构造二叉树的数目
if(start>=end)return 1; //start<end表示空子树， start==end表示叶子节点
int treeNums=0;
for(int root=start; root<=end; root++){
int leftCount = binaryTreeNums(start, root-1); //计算左子树的数目
int rightCount = binaryTreeNums(root+1, end); //计算右子树的数目
treeNums+= leftCount*rightCount;
}
return treeNums;
}
int numTrees(int n) {
if(n==0)return 0;
return binaryTreeNums(1, n);
}
};LeetCode: Unique Binary Search Trees [095],布布扣,bubuko.com
LeetCode: Unique Binary Search Trees [095]
原文地址：http://blog.csdn.net/harryhuang1990/article/details/27958273
