README.md

166. Fraction to Recurring Decimal

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format.

If the fractional part is repeating, enclose the repeating part in parentheses.

If multiple answers are possible, return any of them.

It is guaranteed that the length of the answer string is less than 104 for all the given inputs.

Example 1:

Input: numerator = 1, denominator = 2
Output: "0.5"

Example 2:

Input: numerator = 2, denominator = 1
Output: "2"

Example 3:

Input: numerator = 4, denominator = 333
Output: "0.(012)"

Constraints:

• -231 <= numerator, denominator <= 231 - 1
• denominator != 0

Solutions (Rust)

1. Solution

use std::collections::HashMap;

impl Solution {
    pub fn fraction_to_decimal(numerator: i32, denominator: i32) -> String {
        let negative = numerator != 0 && ((numerator < 0) ^ (denominator < 0));
        let mut numerator = (numerator as i64).abs();
        let denominator = (denominator as i64).abs();
        let mut numerators = HashMap::new();
        let mut fraction = vec![];

        if negative {
            fraction.push(b'-');
        }
        fraction.append(&mut (numerator / denominator).to_string().into_bytes());
        if numerator % denominator != 0 {
            fraction.push(b'.');
        }
        numerator = (numerator % denominator) * 10;

        while numerator > 0 {
            if let Some(&i) = numerators.get(&numerator) {
                fraction.insert(i, b'(');
                fraction.push(b')');
                break;
            } else {
                fraction.push((numerator / denominator) as u8 + b'0');
                numerators.insert(numerator, fraction.len() - 1);
                numerator = (numerator % denominator) * 10;
            }
        }

        String::from_utf8(fraction).unwrap()
    }
}