init

problems/p25/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "p25"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+num-bigint = "0.4.6"

problems/p25/src/main.rs

@@ -0,0 +1,48 @@
+use num_bigint::BigUint;
+use std::collections::HashMap;
+
+struct FibCal {
+    cache: HashMap<u64, BigUint>,
+}
+
+impl FibCal {
+    fn new() -> Self {
+        let mut cache = HashMap::new();
+        cache.insert(0, BigUint::from(0u32));
+        cache.insert(1, BigUint::from(1u32));
+        Self { cache }
+    }
+
+    fn fib(&mut self, n: u64) -> BigUint {
+        if let Some(cached) = self.cache.get(&n) {
+            return cached.clone();
+        }
+        let result = self.fib(n - 1) + self.fib(n - 2);
+        self.cache.insert(n, result.clone());
+        result
+    }
+}
+
+#[test]
+fn test_fib() {
+    let mut fib_cal = FibCal::new();
+
+    assert_eq!(fib_cal.fib(0), BigUint::from(0u32)); // F(0) = 0
+    assert_eq!(fib_cal.fib(1), BigUint::from(1u32)); // F(1) = 1
+    assert_eq!(fib_cal.fib(2), BigUint::from(1u32)); // F(2) = 1
+    assert_eq!(fib_cal.fib(3), BigUint::from(2u32)); // F(3) = 2
+    assert_eq!(fib_cal.fib(4), BigUint::from(3u32)); // F(4) = 3
+}
+
+fn main() {
+    let mut term = 1u64;
+    let mut fib_cal = FibCal::new();
+    loop {
+        let result = fib_cal.fib(term);
+        if result.to_string().len() >= 1000 {
+            break;
+        }
+        term += 1;
+    }
+    println!("{term}");
+}