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class Solution {
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 public:
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  vector<int> plusOne(vector<int> &digits) {
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    int len = digits.size(), carry = 0, temp = 0;
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    vector<int> arr;
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    for (int i = len - 1; i >= 0; i--) { // traverse from back to front
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      temp = digits[i] + carry;
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      if (i == len - 1) {
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        temp++;
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      }
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      arr.push_back(temp % 10);
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      carry = temp / 10;
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    }
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    if (carry) {
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      arr.push_back(carry);
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    }
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    reverse(arr.begin(), arr.end());
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    return arr;
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  }
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};