Longest Ideal Subsequence LeetCode solution in C++

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class Solution {
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 public:
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  int longestIdealString(string s, int k) {
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    int DP[26] = {0}, ans = 1;
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    for (char &ch : s) {
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      int i = ch - 'a';
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      DP[i] = DP[i] + 1;
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      for (int j = max(0, i - k); j <= min(25, i + k); j++)
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        if (j != i) DP[i] = max(DP[i], DP[j] + 1);
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      ans = max(ans, DP[i]);
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    }
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    return ans;
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  }
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};