After lots of trial and error I finally got it, kinda bruteforcy but works, fast

src/bin/problem_26.rs

@@ -1,19 +1,144 @@
-use utils::fraction::Fraction;
+use std::collections::{HashMap, HashSet};
+
+use utils::{
+    fraction::Fraction,
+    number::{Number, Sign},
+};
 
 fn main() {
     println!("Start");
     let mut longest = (0, 0);
-    for denominator in 7..13 {
-        println!("1/{denominator}:");
+    for denominator in 2..1000 {
         let f = Fraction {
             numerator: 1.into(),
             denominator: denominator.into(),
         };
-        let rep = f.get_repeating();
-        if longest.1 < rep.digits.len() {
-            longest = (denominator, rep.digits.len());
+        if let Some(rep) = get_recurring(&f) {
+            if longest.1 < rep.digits.len() {
+                longest = (denominator, rep.digits.len());
+            }
         }
-        println!("{rep}");
     }
     println!("longest {}", longest.0);
 }
+
+pub fn get_recurring(fraction: &Fraction) -> Option<Number> {
+    let mut div_memory = HashMap::new();
+    let mut rem_memory = HashSet::new();
+    rem_memory.insert(1.into());
+    let mut div_with = fraction.numerator.clone();
+    let mut rational = Vec::new();
+    if div_with < fraction.denominator {
+        div_with = div_with * 10;
+    }
+    loop {
+        while div_with < fraction.denominator {
+            rational.push(0);
+            div_memory
+                .entry(0)
+                .and_modify(|value| *value += 1)
+                .or_insert(1);
+            div_with = div_with * 10;
+            rem_memory.insert(div_with.clone());
+        }
+        let (div, rem) =
+            Number::div_with_rem(div_with.clone(), fraction.denominator.clone()).unwrap();
+        if rem == 0.into() {
+            return None;
+        }
+        let next_digit = div.digits[0];
+        if div_memory.contains_key(&next_digit) && rem_memory.contains(&rem) && next_digit != 0 {
+            let mut digits = vec![];
+            if div_memory.values().min() != div_memory.values().max() {
+                rational.push(div.digits[0]);
+                digits = rational;
+                let (l, r) = digits.split_at(digits.len() / 2);
+                if l == r {
+                    digits = l.to_vec();
+                }
+            } else {
+                let idx = rational
+                    .iter()
+                    .position(|digit| digit == &div.digits[0])
+                    .unwrap();
+                if idx == rational.len() - 1 {
+                    digits.push(div.digits[0]);
+                } else {
+                    for digit in &rational[idx..] {
+                        if digits.contains(digit) {
+                            break;
+                        }
+                        digits.push(*digit);
+                    }
+                }
+            }
+            return Some(Number {
+                digits,
+                sign: Sign::Positif,
+            });
+        }
+        div_memory
+            .entry(next_digit)
+            .and_modify(|count| *count += 1)
+            .or_insert(1);
+        rem_memory.insert(rem.clone());
+        rational.push(div.digits[0]);
+        div_with = rem * 10;
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use utils::{fraction::Fraction, number::Number};
+
+    use crate::get_recurring;
+
+    #[test]
+    fn test_1_div_2() {
+        let f = Fraction::new(1.into(), 2.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, None);
+    }
+
+    #[test]
+    fn test_1_div_6() {
+        let f = Fraction::new(1.into(), 6.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("6")));
+    }
+
+    #[test]
+    fn test_1_div_7() {
+        let f = Fraction::new(1.into(), 7.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("142857")));
+    }
+
+    #[test]
+    fn test_1_div_11() {
+        let f = Fraction::new(1.into(), 11.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("09")));
+    }
+
+    #[test]
+    fn test_1_div_12() {
+        let f = Fraction::new(1.into(), 12.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("3")));
+    }
+
+    #[test]
+    fn test_1_div_14() {
+        let f = Fraction::new(1.into(), 14.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("714285")));
+    }
+
+    #[test]
+    fn test_1_div_101() {
+        let f = Fraction::new(1.into(), 101.into()).unwrap();
+        let rep = get_recurring(&f);
+        assert_eq!(rep, Some(Number::from("0099")));
+    }
+}