Finding the Users Active Minutes LeetCode solution in Java

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class Solution {
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  public int[] findingUsersActiveMinutes(int[][] logs, int k) {
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    // create a hashmap to record the ids of users
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    // and a set to store the minutes in which they were active
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    Map<Integer, Set<Integer>> map = new HashMap<>();
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    for (int[] l : logs) {
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      // l[0] -> id, l[1] -> active minute
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      map.putIfAbsent(l[0], new HashSet<>()); // if new id
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      map.get(l[0]).add(l[1]); // add the minute of activeness to the set
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    }
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    // create answer array
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    int[] ans = new int[k];
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    for (int id : map.keySet()) {
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      // the set contains all the minutes in which the id was active
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      // so the set size will be the number of active minutes
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      // or the 'User Active Minutes' (UAM)
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      int uam = map.get(id).size();
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      // each index in ans array is a UAM,
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      // and we need to put the number of users having that UAM
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      // whenever we enocunter a UAM, we increment the value in array
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      // which means we have found one more user with the same UAM
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      ans[uam - 1]++; // since array is 1 based indexing, we substract 1
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    }
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    return ans; // return ans array
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  }
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}