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class Solution {
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  public String reverseVowels(String s) {
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    Set<Character> set = new HashSet<>();
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    set.add('a');
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    set.add('e');
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    set.add('i');
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    set.add('o');
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    set.add('u');
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    set.add('A');
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    set.add('E');
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    set.add('I');
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    set.add('O');
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    set.add('U');
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    StringBuilder str = new StringBuilder(s);
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    int left = 0, right = str.length() - 1;
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    while (left < right) {
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      if (!set.contains(str.charAt(left))) {
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        left++;
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      }
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      if (!set.contains(str.charAt(right))) {
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        right--;
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      }
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      if (set.contains(str.charAt(left)) && set.contains(s.charAt(right))) {
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        char temp = str.charAt(left);
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        str.setCharAt(left++, str.charAt(right));
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        str.setCharAt(right--, temp);
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      }
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    }
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    return str.toString();
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  }
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}