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1507. Reformat Date

Description

Given a date string in the form Day Month Year, where:

  • Day is in the set {"1st", "2nd", "3rd", "4th", ..., "30th", "31st"}.
  • Month is in the set {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}.
  • Year is in the range [1900, 2100].

Convert the date string to the format YYYY-MM-DD, where:

  • YYYY denotes the 4 digit year.
  • MM denotes the 2 digit month.
  • DD denotes the 2 digit day.

 

Example 1:

Input: date = "20th Oct 2052"
Output: "2052-10-20"

Example 2:

Input: date = "6th Jun 1933"
Output: "1933-06-06"

Example 3:

Input: date = "26th May 1960"
Output: "1960-05-26"

 

Constraints:

  • The given dates are guaranteed to be valid, so no error handling is necessary.

Solutions

Solution 1

Thinking

The input is always “day month year” and the output is \(YYYY\)-\(MM\)-\(DD\). There is no search or DP; we only rewrite the three fields.

Split on spaces and reverse so the year sits first. Locate the month in a concatenated abbreviation string; the index divided by \(3\), plus one, is the month number. Strip the day suffix and pad both month and day. Joining with hyphens yields the canonical date.

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class Solution:
    def reformatDate(self, date: str) -> str:
        s = date.split()
        s.reverse()
        months = " JanFebMarAprMayJunJulAugSepOctNovDec"
        s[1] = str(months.index(s[1]) // 3 + 1).zfill(2)
        s[2] = s[2][:-2].zfill(2)
        return "-".join(s)

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class Solution {
    public String reformatDate(String date) {
        var s = date.split(" ");
        String months = " JanFebMarAprMayJunJulAugSepOctNovDec";
        int day = Integer.parseInt(s[0].substring(0, s[0].length() - 2));
        int month = months.indexOf(s[1]) / 3 + 1;
        return String.format("%s-%02d-%02d", s[2], month, day);
    }
}

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class Solution {
public:
    string reformatDate(string date) {
        string months = " JanFebMarAprMayJunJulAugSepOctNovDec";
        stringstream ss(date);
        string year, month, t;
        int day;
        ss >> day >> t >> month >> year;
        month = to_string(months.find(month) / 3 + 1);
        return year + "-" + (month.size() == 1 ? "0" + month : month) + "-" + (day > 9 ? "" : "0") + to_string(day);
    }
};

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func reformatDate(date string) string {
    s := strings.Split(date, " ")
    day, _ := strconv.Atoi(s[0][:len(s[0])-2])
    months := " JanFebMarAprMayJunJulAugSepOctNovDec"
    month := strings.Index(months, s[1])/3 + 1
    year, _ := strconv.Atoi(s[2])
    return fmt.Sprintf("%d-%02d-%02d", year, month, day)
}

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function reformatDate(date: string): string {
    const s = date.split(' ');
    const months = ' JanFebMarAprMayJunJulAugSepOctNovDec';
    const day = parseInt(s[0].substring(0, s[0].length - 2));
    const month = Math.floor(months.indexOf(s[1]) / 3) + 1;
    return `${s[2]}-${month.toString().padStart(2, '0')}-${day.toString().padStart(2, '0')}`;
}

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class Solution {
    /**
     * @param String $date
     * @return String
     */
    function reformatDate($date) {
        $arr = explode(' ', $date);
        $months = [
            'Jan' => '01',
            'Feb' => '02',
            'Mar' => '03',
            'Apr' => '04',
            'May' => '05',
            'Jun' => '06',
            'Jul' => '07',
            'Aug' => '08',
            'Sep' => '09',
            'Oct' => '10',
            'Nov' => '11',
            'Dec' => '12',
        ];
        $year = $arr[2];
        $month = $months[$arr[1]];
        $day = intval($arr[0]);
        if ($day > 0 && $day < 10) {
            $day = '0' . $day;
        }
        return $year . '-' . $month . '-' . $day;
    }
}

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