java 解法, 执行用时: 1 ms, 内存消耗: 39.1 MB, 提交时间: 2022-12-04 14:13:28

class Solution {
    public String fractionToDecimal(int numerator, int denominator) {
        long numeratorLong = (long) numerator;
        long denominatorLong = (long) denominator;
        if (numeratorLong % denominatorLong == 0) {
            return String.valueOf(numeratorLong / denominatorLong);
        }

        StringBuffer sb = new StringBuffer();
        if (numeratorLong < 0 ^ denominatorLong < 0) {
            sb.append('-');
        }

        // 整数部分
        numeratorLong = Math.abs(numeratorLong);
        denominatorLong = Math.abs(denominatorLong);
        long integerPart = numeratorLong / denominatorLong;
        sb.append(integerPart);
        sb.append('.');

        // 小数部分
        StringBuffer fractionPart = new StringBuffer();
        Map<Long, Integer> remainderIndexMap = new HashMap<Long, Integer>();
        long remainder = numeratorLong % denominatorLong;
        int index = 0;
        while (remainder != 0 && !remainderIndexMap.containsKey(remainder)) {
            remainderIndexMap.put(remainder, index);
            remainder *= 10;
            fractionPart.append(remainder / denominatorLong);
            remainder %= denominatorLong;
            index++;
        }
        if (remainder != 0) { // 有循环节
            int insertIndex = remainderIndexMap.get(remainder);
            fractionPart.insert(insertIndex, '(');
            fractionPart.append(')');
        }
        sb.append(fractionPart.toString());

        return sb.toString();
    }
}

javascript 解法, 执行用时: 64 ms, 内存消耗: 41.3 MB, 提交时间: 2022-12-04 14:13:08

/**
 * @param {number} numerator
 * @param {number} denominator
 * @return {string}
 */
var fractionToDecimal = function(numerator, denominator) {
    if (numerator % denominator == 0) {
        return '' + Math.floor(numerator / denominator);
    }

    const sb = [];
    if (numerator < 0 ^ denominator < 0) {
        sb.push('-');
    }

    // 整数部分
    numerator = Math.abs(numerator);
    denominator = Math.abs(denominator);
    const integerPart = Math.floor(numerator / denominator);
    sb.push(integerPart);
    sb.push('.');

    // 小数部分
    const fractionPart = [];
    const remainderIndexDic = new Map();
    let remainder = numerator % denominator;
    let index = 0;
    while (remainder !== 0 && !remainderIndexDic.has(remainder)) {
        remainderIndexDic.set(remainder, index);
        remainder *= 10;
        fractionPart.push(Math.floor(remainder / denominator));
        remainder %= denominator;
        index++;
    }
    if (remainder !== 0) { // 有循环节
        let insertIndex = remainderIndexDic.get(remainder);
        fractionPart.splice(insertIndex, 0, '(');
        fractionPart.push(')');
    }
    sb.push(fractionPart.join(''));

    return sb.join('');
}

golang 解法, 执行用时: 0 ms, 内存消耗: 2 MB, 提交时间: 2022-12-04 14:12:53

func fractionToDecimal(numerator, denominator int) string {
    if numerator%denominator == 0 {
        return strconv.Itoa(numerator / denominator)
    }

    s := []byte{}
    if numerator < 0 != (denominator < 0) {
        s = append(s, '-')
    }

    // 整数部分
    numerator = abs(numerator)
    denominator = abs(denominator)
    integerPart := numerator / denominator
    s = append(s, strconv.Itoa(integerPart)...)
    s = append(s, '.')

    // 小数部分
    indexMap := map[int]int{}
    remainder := numerator % denominator
    for remainder != 0 && indexMap[remainder] == 0 {
        indexMap[remainder] = len(s)
        remainder *= 10
        s = append(s, '0'+byte(remainder/denominator))
        remainder %= denominator
    }
    if remainder > 0 { // 有循环节
        insertIndex := indexMap[remainder]
        s = append(s[:insertIndex], append([]byte{'('}, s[insertIndex:]...)...)
        s = append(s, ')')
    }

    return string(s)
}

func abs(x int) int {
    if x < 0 {
        return -x
    }
    return x
}

python3 解法, 执行用时: 44 ms, 内存消耗: 15.1 MB, 提交时间: 2022-12-04 14:12:36

class Solution:
    def fractionToDecimal(self, numerator: int, denominator: int) -> str:
        if numerator % denominator == 0:
            return str(numerator // denominator)

        s = []
        if (numerator < 0) != (denominator < 0):
            s.append('-')

        # 整数部分
        numerator = abs(numerator)
        denominator = abs(denominator)
        integerPart = numerator // denominator
        s.append(str(integerPart))
        s.append('.')

        # 小数部分
        indexMap = {}
        remainder = numerator % denominator
        while remainder and remainder not in indexMap:
            indexMap[remainder] = len(s)
            remainder *= 10
            s.append(str(remainder // denominator))
            remainder %= denominator
        if remainder:  # 有循环节
            insertIndex = indexMap[remainder]
            s.insert(insertIndex, '(')
            s.append(')')

        return ''.join(s)