[LeetCode]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.

For example,

• Given numerator = 1, denominator = 2, return "0.5".
• Given numerator = 2, denominator = 1, return "2".
• Given numerator = 2, denominator = 3, return "0.(6)".

Credits:
Special thanks to @Shangrila for adding this problem and creating all test cases.

public class Solution {class Pair{@Overridepublic int hashCode() {final int prime = 31;int result = 1;result = prime * result + getOuterType().hashCode();result = prime * result + ans;result = prime * result + mod;return result;}@Overridepublic boolean equals(Object obj) {if (this == obj)return true;if (obj == null)return false;if (getClass() != obj.getClass())return false;Pair other = (Pair) obj;if (!getOuterType().equals(other.getOuterType()))return false;if (ans != other.ans)return false;if (mod != other.mod)return false;return true;}int mod;int ans;Pair(int mod,int ans){this.mod = mod;this.ans = ans;}private Solution getOuterType() {return Solution.this;}}    public String fractionToDecimal(int numerator, int denominator) {        if(numerator == 0) return "0";        int ans = numerator/denominator;        int mod = numerator%denominator;        if(mod == 0) return ans+"";        StringBuilder sb = new StringBuilder();        sb.append(ans+".");        Map<Pair,Integer> map = new HashMap<>();        while(mod!=0){        ans = (10*mod)/denominator;        mod = (10*mod)%denominator;        Pair p = new Pair(mod,ans);        if(map.containsKey(p)){        sb.insert(map.get(p)-1, "(");        sb.append(")");        break;        }else if(mod == 0){        sb.append(ans);        break;        }        sb.append(ans);        map.put(p, sb.length());        }        return sb.toString();    }}