LeetCode-in-All
96. Unique Binary Search Trees
Medium
Given an integer n, return the number of structurally unique BST’s (binary search trees) which has exactly n nodes of unique values from 1 to n.
Example 1:
Input: n = 3
Output: 5
Example 2:
Input: n = 1
Output: 1
Constraints:
1 <= n <= 19
Solution
func numTrees(n int) int {
result := 1
for i := 0; i < n; i++ {
result *= 2*n - i
result /= i + 1
}
result /= n + 1
return result
}