Tags: "leetcode", "sort", "comparator", access_time 2-min read

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Reorder Data in Log Files

Created: November 8, 2019 by [lek-tin]

Last updated: November 8, 2019

You have an array of logs. Each log is a space delimited string of words.

For each log, the first word in each log is an alphanumeric identifier. Then, either:

Each word after the identifier will consist only of lowercase letters, or; Each word after the identifier will consist only of digits. We will call these two varieties of logs letter-logs and digit-logs. It is guaranteed that each log has at least one word after its identifier.

Reorder the logs so that all of the letter-logs come before any digit-log. The letter-logs are ordered lexicographically ignoring identifier, with the identifier used in case of ties. The digit-logs should be put in their original order.

Return the final order of the logs.

Example 1:

Input: ["a1 9 2 3 1","g1 act car","zo4 4 7","ab1 off key dog","a8 act zoo"]
Output: ["g1 act car","a8 act zoo","ab1 off key dog","a1 9 2 3 1","zo4 4 7"]


  1. 0 <= logs.length <= 1001
  2. 3 <= logs[i].length <= 100
  3. logs[i] is guaranteed to have an identifier, and a word after the identifier.


Java comparator

class Solution {

    private class logComparator implements Comparator<String> {
        public int compare(String a, String b) {
            int index_a = a.indexOf(" ") + 1;
            int index_b = b.indexOf(" ") + 1;
            char char_a = a.charAt(index_a);
            char char_b = b.charAt(index_b);
            // If both are char, compare by substirng
            if (!isDigit(char_a) && !isDigit(char_b)) {
                return a.substring(index_a).compareTo(b.substring(index_b));
            // char should appear before digit, return negative value;
            if (!isDigit(char_a) && isDigit(char_b)) {
                return -1;
            // char should be brought forward, return positive value;
            if (isDigit(char_a) && !isDigit(char_b)) {
                return 1;
            // If both are digits, remain order
            return 0;

    private boolean isDigit(char ch) {
      if(ch >= '0' && ch <= '9') return true;
      else return false;

    public String[] reorderLogFiles(String[] logs) {
        logComparator LC = new logComparator();
        Arrays.sort(logs, LC);

        return logs;


class Solution(object):
    def reorderLogFiles(self, logs):
        :type logs: List[str]
        :rtype: List[str]
        def f(log):
            i, content = log.split(" ", 1)
            return (0, content, i) if content[0].isalpha() else (1,)

        return logs