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class Solution {
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  public TreeNode recoverFromPreorder(String traversal) {
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    if (!traversal.contains("-")) return new TreeNode(Integer.parseInt(traversal));
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    String number = "";
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    int i = 0;
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    while (traversal.charAt(i) != '-') {
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      number += traversal.charAt(i);
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      i++;
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    }
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    // System.out.print("root = " + number + " " + i + "     ");
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    TreeNode root = new TreeNode(Integer.parseInt(number));
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    StringBuilder str = new StringBuilder();
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    int bk = 0;
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    for (int j = i; i < traversal.length(); i++) {
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      if (traversal.charAt(i - 1) != '-'
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          && traversal.charAt(i) == '-'
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          && traversal.charAt(i + 1) != '-') bk = str.toString().length();
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      else if (!(traversal.charAt(i - 1) != '-' && traversal.charAt(i) == '-'))
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        str.append(traversal.charAt(i));
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    }
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    String divide = str.toString();
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    TreeNode left =
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        (bk == 0) ? recoverFromPreorder(divide) : recoverFromPreorder(divide.substring(0, bk));
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    TreeNode right = (bk == 0) ? null : recoverFromPreorder(divide.substring(bk, divide.length()));
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    root.left = left;
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    root.right = right;
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    return root;
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  }
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}