From 3374c9ff35651388d49db704f3f76e6f736d07d6 Mon Sep 17 00:00:00 2001
From: Nilstrieb <48135649+Nilstrieb@users.noreply.github.com>
Date: Sun, 23 Jan 2022 22:03:24 +0100
Subject: [PATCH] tree

---
 src/lib.rs | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/lib.rs b/src/lib.rs
index 83d2737..0741f1e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,5 @@
+//! https://www.baeldung.com/java-monte-carlo-tree-search
+
 #![allow(dead_code)]
 
 use bumpalo::collections::Vec;
@@ -85,7 +87,7 @@ mod mcts {
     }
 
     fn expand_node<S>(node: &Node<S>) {
-        todo!()
+        todo!("next")
     }
 
     fn simulate_random_playout<S>(node: &Node<'_, S>) -> u64 {
@@ -95,6 +97,30 @@ mod mcts {
     fn back_propagation<S>(node: &Node<'_, S>, playout_result: u64) {
         todo!()
     }
+
+    mod uct {
+        use crate::Node;
+
+        pub fn uct(total_visit: u64, win_score: u64, node_visit: u64) -> u64 {
+            if node_visit == 0 {
+                return u64::MAX;
+            }
+
+            let num = (win_score / node_visit) as f64
+                + std::f64::consts::SQRT_2
+                    * f64::sqrt((total_visit as f64).ln() / node_visit as f64);
+
+            num as u64
+        }
+
+        pub fn find_best_node_with_uct<S>(node: &Node<S>) -> Option<&Node<S>> {
+            let parent_visit_count = node.visited;
+
+            node.children
+                .iter()
+                .max_by_key(|n| uct(parent_visit_count, n.won, n.visited))
+        }
+    }
 }
 
 #[cfg(test)]