From c419c72b137b043d831c595166ad3aefc1dc8a97 Mon Sep 17 00:00:00 2001
From: Libin YANG <contact@yanglibin.info>
Date: Wed, 24 Sep 2025 06:54:25 +0800
Subject: [PATCH] feat: add rust solution to lc problem: No.0166

---
 .../README.md                                 | 47 +++++++++++++++++++
 .../README_EN.md                              | 47 +++++++++++++++++++
 .../Solution.rs                               | 42 +++++++++++++++++
 3 files changed, 136 insertions(+)
 create mode 100644 solution/0100-0199/0166.Fraction to Recurring Decimal/Solution.rs

diff --git a/solution/0100-0199/0166.Fraction to Recurring Decimal/README.md b/solution/0100-0199/0166.Fraction to Recurring Decimal/README.md
index bf98e9ad90c86..ac50e36c63997 100644
--- a/solution/0100-0199/0166.Fraction to Recurring Decimal/README.md	
+++ b/solution/0100-0199/0166.Fraction to Recurring Decimal/README.md	
@@ -262,6 +262,53 @@ function fractionToDecimal(numerator: number, denominator: number): string {
 }
 ```
 
+#### Rust
+
+```rust
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn fraction_to_decimal(numerator: i32, denominator: i32) -> String {
+        if numerator == 0 {
+            return "0".to_string();
+        }
+        let mut ans = String::new();
+
+        let neg = (numerator > 0) ^ (denominator > 0);
+        if neg {
+            ans.push('-');
+        }
+
+        let mut a = (numerator as i64).abs();
+        let b = (denominator as i64).abs();
+
+        ans.push_str(&(a / b).to_string());
+        a %= b;
+
+        if a == 0 {
+            return ans;
+        }
+
+        ans.push('.');
+
+        let mut d: HashMap<i64, usize> = HashMap::new();
+        while a != 0 {
+            if let Some(&pos) = d.get(&a) {
+                ans.insert(pos, '(');
+                ans.push(')');
+                break;
+            }
+            d.insert(a, ans.len());
+            a *= 10;
+            ans.push_str(&(a / b).to_string());
+            a %= b;
+        }
+
+        ans
+    }
+}
+```
+
 #### C#
 
 ```cs
diff --git a/solution/0100-0199/0166.Fraction to Recurring Decimal/README_EN.md b/solution/0100-0199/0166.Fraction to Recurring Decimal/README_EN.md
index acf8ab93d3724..92720f7b792b2 100644
--- a/solution/0100-0199/0166.Fraction to Recurring Decimal/README_EN.md	
+++ b/solution/0100-0199/0166.Fraction to Recurring Decimal/README_EN.md	
@@ -260,6 +260,53 @@ function fractionToDecimal(numerator: number, denominator: number): string {
 }
 ```
 
+#### Rust
+
+```rust
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn fraction_to_decimal(numerator: i32, denominator: i32) -> String {
+        if numerator == 0 {
+            return "0".to_string();
+        }
+        let mut ans = String::new();
+
+        let neg = (numerator > 0) ^ (denominator > 0);
+        if neg {
+            ans.push('-');
+        }
+
+        let mut a = (numerator as i64).abs();
+        let b = (denominator as i64).abs();
+
+        ans.push_str(&(a / b).to_string());
+        a %= b;
+
+        if a == 0 {
+            return ans;
+        }
+
+        ans.push('.');
+
+        let mut d: HashMap<i64, usize> = HashMap::new();
+        while a != 0 {
+            if let Some(&pos) = d.get(&a) {
+                ans.insert(pos, '(');
+                ans.push(')');
+                break;
+            }
+            d.insert(a, ans.len());
+            a *= 10;
+            ans.push_str(&(a / b).to_string());
+            a %= b;
+        }
+
+        ans
+    }
+}
+```
+
 #### C#
 
 ```cs
diff --git a/solution/0100-0199/0166.Fraction to Recurring Decimal/Solution.rs b/solution/0100-0199/0166.Fraction to Recurring Decimal/Solution.rs
new file mode 100644
index 0000000000000..f10d6f00b14b7
--- /dev/null
+++ b/solution/0100-0199/0166.Fraction to Recurring Decimal/Solution.rs	
@@ -0,0 +1,42 @@
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn fraction_to_decimal(numerator: i32, denominator: i32) -> String {
+        if numerator == 0 {
+            return "0".to_string();
+        }
+        let mut ans = String::new();
+
+        let neg = (numerator > 0) ^ (denominator > 0);
+        if neg {
+            ans.push('-');
+        }
+
+        let mut a = (numerator as i64).abs();
+        let b = (denominator as i64).abs();
+
+        ans.push_str(&(a / b).to_string());
+        a %= b;
+
+        if a == 0 {
+            return ans;
+        }
+
+        ans.push('.');
+
+        let mut d: HashMap<i64, usize> = HashMap::new();
+        while a != 0 {
+            if let Some(&pos) = d.get(&a) {
+                ans.insert(pos, '(');
+                ans.push(')');
+                break;
+            }
+            d.insert(a, ans.len());
+            a *= 10;
+            ans.push_str(&(a / b).to_string());
+            a %= b;
+        }
+
+        ans
+    }
+}