[LeetCode] 937. Reorder Data in Log Files 日志文件的重新排序

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: logs = ["dig1 8 1 5 1","let1 art can","dig2 3 6","let2 own kit dig","let3 art zero"]
Output: ["let1 art can","let3 art zero","let2 own kit dig","dig1 8 1 5 1","dig2 3 6"]

Constraints:

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

這道題讓給日志排序，每條日志是由空格隔開的一些字符串，第一個字符串是標識符，可能由字母和數字組成，后面的是日志的內容，只有兩種形式的，要么都是數字的，要么都是字母的。排序的規則是對於內容是字母的日志，按照字母順序進行排序，假如內容相同，則按照標識符的字母順序排。而對於內容的是數字的日志，放到最后面，且其順序相對於原順序保持不變。博主感覺這道題似曾相識啊，貌似之前在很多 OA 中見過，最后還是被 LeetCode 收入囊中了。其實這道題就是個比較復雜的排序的問題，兩種日志需要分開處理，對於數字日志，不需要排序，但要記錄其原始順序。這里就可以用一個數組專門來保存數字日志，這樣最后加到結果 res 后面，就可以保持其原來順序。關鍵是要對字母型日志進行排序，同時還要把標識符提取出來，這樣在遍歷日志的時候，先找到第一空格的位置，這樣前面的部分就是標識符了，后面的內容就是日志內容了，此時判斷緊跟空格位置的字符，假如是數字的話，說明當前日志是數字型的，加入數組 digitLogs 中，並繼續循環。如果不是的話，將兩部分分開，存入到一個二維數組 data 中。之后要對 data 數組進行排序，並需要重寫排序規則，要根據日志內容排序，若日志內容相等，則根據標識符排序。最后把排序好的日志按順序合並，存入結果 res 中，最后別忘了把數字型日志也加入 res， 參見代碼如下：

class Solution {
public:
    vector<string> reorderLogFiles(vector<string>& logs) {
        vector<string> res, digitLogs;
        vector<vector<string>> data;
        for (string log : logs) {
            auto pos = log.find(" ");
            if (log[pos + 1] >= '0' && log[pos + 1] <= '9') {
                digitLogs.push_back(log);
                continue;
            }
            data.push_back({log.substr(0, pos), log.substr(pos + 1)});
        }
        sort(data.begin(), data.end(), [](vector<string>& a, vector<string>& b) {
            return a[1] < b[1] || (a[1] == b[1] && a[0] < b[0]);
        });
        for (auto &a : data) {
            res.push_back(a[0] + " " + a[1]);
        }
        for (string log : digitLogs) res.push_back(log);
        return res;
    }
};

參考資料：

https://leetcode.com/problems/reorder-data-in-log-files/

https://leetcode.com/problems/reorder-data-in-log-files/discuss/192438/C%2B%2B-O(NlogN)-Time-O(N)-Space

https://leetcode.com/problems/reorder-data-in-log-files/discuss/193656/C%2B%2B-stable_sort-easy-to-understand

https://leetcode.com/problems/reorder-data-in-log-files/discuss/193872/Java-Nothing-Fancy-15-lines-2ms-all-clear.

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