feat: add initial implementation of new 21 game solution

837_new_21_game/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "new_21_game"
+version = "0.1.0"

837_new_21_game/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "new_21_game"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]

837_new_21_game/src/main.rs

@@ -0,0 +1,35 @@
+fn main() {
+    println!("Hello, world!");
+}
+
+struct Solution;
+
+impl Solution {
+    pub fn new21_game(n: i32, k: i32, max_pts: i32) -> f64 {
+        if k == 0 || n >= k + max_pts {
+            return 1f64;
+        }
+
+        let mut result = 0f64;
+        let mut table = vec![0f64; (n + 1) as usize];
+        table[0] = 1f64;
+        let mut sum = 1f64;
+
+        for i in 1..(n + 1) {
+            let prob = sum / max_pts as f64;
+            table[i as usize] = prob;
+
+            if i < k {
+                sum += prob;
+            } else {
+                result += prob;
+            }
+
+            if i >= max_pts {
+                sum -= table[(i - max_pts) as usize];
+            }
+        }
+
+        result
+    }
+}