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class Solution {
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  public int compress(char[] chars) {
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    int index = 0;
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    int i = 0;
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    while (i < chars.length) {
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      int j = i;
8

9
      while (j < chars.length && chars[j] == chars[i]) {
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        j++;
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      }
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      chars[index++] = chars[i];
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      if (j - i > 1) {
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        String count = j - i + "";
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        for (char c : count.toCharArray()) {
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          chars[index++] = c;
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        }
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      }
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      i = j;
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    }
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    return index;
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  }
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}
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// TC: O(n), SC: O(1)