635. Design Log Storage System

Explanation:

To design a log storage system, we can use a data structure that allows us to store logs and query logs based on a given range of timestamps. One approach is to use a TreeMap where we store the logs with their timestamps as keys. This will allow us to efficiently query logs within a given time range.

Algorithmic Idea:

Use a TreeMap to store logs with timestamps as keys.
For each log operation, insert the log with its timestamp into the TreeMap.
When querying logs within a time range, iterate through the TreeMap and filter logs within the given range.

Time Complexity:

Inserting a log: O(log n) where n is the number of logs.
Querying logs within a time range: O(n) where n is the number of logs within the given range.

Space Complexity:

O(n) where n is the number of logs stored in the TreeMap.

: :

View Leetcode Problem

import java.util.TreeMap;

class LogSystem {
    TreeMap<Long, String> logs;

    public LogSystem() {
        logs = new TreeMap<>();
    }

    public void put(int id, String timestamp) {
        logs.put(Long.parseLong(timestamp.replace(":", "")), String.valueOf(id));
    }

    public List<Integer> retrieve(String s, String e, String gra) {
        long start = getStartTime(s, gra);
        long end = getEndTime(e, gra);
        List<Integer> result = new ArrayList<>();

        for (Map.Entry<Long, String> entry : logs.subMap(start, true, end, true).entrySet()) {
            result.add(Integer.parseInt(entry.getValue()));
        }

        return result;
    }

    private long getStartTime(String timestamp, String gra) {
        timestamp = timestamp.replace(":", "");
        if (gra.equals("Year")) {
            return Long.parseLong(timestamp.substring(0, 4) + "0000000000");
        } else if (gra.equals("Month")) {
            return Long.parseLong(timestamp.substring(0, 6) + "00000000");
        } else if (gra.equals("Day")) {
            return Long.parseLong(timestamp.substring(0, 8) + "000000");
        } else if (gra.equals("Hour")) {
            return Long.parseLong(timestamp.substring(0, 10) + "0000");
        } else if (gra.equals("Minute")) {
            return Long.parseLong(timestamp.substring(0, 12) + "00");
        } else {
            return Long.parseLong(timestamp);
        }
    }

    private long getEndTime(String timestamp, String gra) {
        timestamp = timestamp.replace(":", "");
        if (gra.equals("Year")) {
            return Long.parseLong(timestamp.substring(0, 4) + "1231235959");
        } else if (gra.equals("Month")) {
            return Long.parseLong(timestamp.substring(0, 6) + "31235959");
        } else if (gra.equals("Day")) {
            return Long.parseLong(timestamp.substring(0, 8) + "235959");
        } else if (gra.equals("Hour")) {
            return Long.parseLong(timestamp.substring(0, 10) + "5959");
        } else if (gra.equals("Minute")) {
            return Long.parseLong(timestamp.substring(0, 12) + "59");
        } else {
            return Long.parseLong(timestamp);
        }
    }
}

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