init

problems/p26/src/main.rs

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+// 分数分为有限小数与无限循环小数
+//
+// 除数不变，当被除数出现相同时，出现循环
+use std::collections::HashSet;
+
+fn div_to_vec(denominator: u32) -> Vec<u32> {
+    let mut remainder_set: HashSet<u32> = HashSet::new();
+    let deno_digits = denominator.to_string().len() as u32;
+    let mut remainder = 10u32.pow(deno_digits);
+    remainder_set.insert(1);
+
+    let mut xiaoshu = Vec::new();
+    let mut divider = remainder / denominator;
+    xiaoshu.push(divider);
+    remainder %= denominator;
+    remainder_set.insert(remainder);
+    while remainder != 0 {
+        remainder *= 10u32.pow(deno_digits);
+        divider = remainder / denominator;
+        xiaoshu.push(divider);
+        remainder %= denominator;
+        if remainder_set.contains(&remainder) {
+            remainder *= 10u32.pow(deno_digits);
+            divider = remainder / denominator;
+            xiaoshu.push(divider);
+            break;
+        }
+        remainder_set.insert(remainder);
+    }
+    xiaoshu
+}
+#[test]
+fn test_div_to_vec() {
+    assert_eq!(div_to_vec(2), vec![5]);
+    assert_eq!(div_to_vec(4), vec![2, 5]);
+    assert_eq!(div_to_vec(5), vec![2]);
+}
+
+fn get_recurring_cycles(denominator: u32) -> u32 {
+    let xiaoshu = div_to_vec(denominator);
+    let last_element = xiaoshu[xiaoshu.len() - 1];
+    let first_idx = xiaoshu.iter().position(|x| x == &last_element).unwrap();
+    let result = xiaoshu.len() - 1 - first_idx;
+    result as u32
+}
+#[test]
+fn test_get_recurring_cycles() {
+    assert_eq!(get_recurring_cycles(6), 1);
+    assert_eq!(get_recurring_cycles(7), 6);
+    assert_ne!(get_recurring_cycles(9), 1);
+    assert_eq!(get_recurring_cycles(11), 2);
+    assert_eq!(get_recurring_cycles(12), 1);
+}
+
+fn main() {
+    let mut longest_cycles = 0;
+    for denominator in 1..1000 {
+        let cycles = get_recurring_cycles(denominator);
+        if cycles > longest_cycles {
+            longest_cycles = cycles;
+        }
+    }
+
+    println!("longest_cycles: {longest_cycles}");
+    // FIX: answer incorrect
+}