Monotone Increasing Digits LeetCode solution in C++

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class Solution {
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 public:
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  int monotoneIncreasingDigits(int n) {
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    if (n < 10) return n;
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    string s = to_string(n);
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    for (int i = s.size() - 2; i >= 0; i--) {
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      if (s[i] > s[i + 1]) {
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        s[i]--;
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        for (int j = i + 1; j < s.size(); j++) s[j] = '9';
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      }
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    }
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    int ans = stoi(s);
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    return ans;
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  }
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};