From 1b5884ab3905fc3569d7b48e077a0b3a9ae24f67 Mon Sep 17 00:00:00 2001 From: crupest Date: Wed, 22 Jul 2020 20:23:08 +0800 Subject: import(solutions): Add problem 96 . --- works/solutions/cpp/96.cpp | 14 ++++++++++++++ 1 file changed, 14 insertions(+) create mode 100644 works/solutions/cpp/96.cpp (limited to 'works/solutions/cpp/96.cpp') diff --git a/works/solutions/cpp/96.cpp b/works/solutions/cpp/96.cpp new file mode 100644 index 0000000..a67a59a --- /dev/null +++ b/works/solutions/cpp/96.cpp @@ -0,0 +1,14 @@ +class Solution { +public: + // catalan number: + // f(n) = f(0) * f(n-1) + f(1) * f(n-2) + ... + f(n-1)*f(0) + // f(n) = 2(2n-1) * f(n-1) / (n+1) + // f(n) = C(2n, n) / (n+1) + int numTrees(int n) { + long long result = 1; + for (int i = 2; i <= n; i++) { + result = 2 * (2 * i - 1) * result / (i + 1); + } + return result; + } +}; -- cgit v1.2.3