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class Solution {
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  public int removeDuplicates(int[] arr) {
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    int i = 0;
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    for (int j = 1; j < arr.length; j++) {
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      if (arr[i] != arr[j]) {
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        i++;
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        arr[i] = arr[j];
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      }
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    }
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    return i + 1;
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  }
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}