Count Lattice Points Inside a Circle LeetCode solution in Java

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class Solution {
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  public int countLatticePoints(int[][] circles) {
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    Set<String> answer = new HashSet<String>();
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    for (int[] c : circles) {
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      int x = c[0], y = c[1], r = c[2];
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      // traversing over all the points that lie inside the smallest square capable of containing
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      // the whole circle
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      for (int xx = x - r; xx <= x + r; xx++)
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        for (int yy = y - r; yy <= y + r; yy++)
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          if ((r * r) >= ((x - xx) * (x - xx)) + ((y - yy) * (y - yy))) answer.add(xx + ":" + yy);
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    }
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    return answer.size();
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  }
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}