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Leetcode166-fractionToRecurringDecimal

Posted on Edited on In Views: Valine:
Solution Report of LeetCode Acceptted

Description

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.

Example

Example 1:

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

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

Example 3:
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Input: numerator = 2, denominator = 3
Output: "0.(6)"

Solution

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class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        if (numerator == 0) return "0";
        StringBuilder res = new StringBuilder();
        res.append((numerator > 0) ^ (denominator > 0) ? "-" : "");
        long num = Math.abs((long)numerator);
        long den = Math.abs((long)denominator);
        
//      integral part
        res.append(num / den);
        num %= den;
        if (num == 0) 
            return res.toString();
        
//      fraction part
        res.append(".");
        HashMap<Long, Integer> map = new HashMap<>();
        map.put(num, res.length());
        while(num > 0){
            num *= 10;
            res.append(num / den);
            num %= den;
            if (map.containsKey(num)){
                res.insert(map.get(num), "(");
                res.append(")");
                break;
            }
            else map.put(num, res.length());
        }
        
        return res.toString();
    }
}