1456. Maximum Number of Vowels in a Substring of Given Length

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problem

solution

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class Solution {
public:
    bool isVowel(char c)
    {
        return c=='a' || c=='e' || c=='i' || c=='o' || c=='u';
    }
    int maxVowels(string s, int k) {
        int l=0, r= 0, n=s.size();
        unordered_map<char, int> mp;
        int mp_size = 0;
        int ret = 0;
        while(r<n)
        {
            char c = s[r++];
            if(isVowel(c) ){
                mp[c]++;
                mp_size ++;
            }
            if(r-l== k)
            {
                ret = max(ret, mp_size);
                char d = s[l++];
                if(isVowel(d)){
                    mp[d]--;
                    mp_size--;
                }
            }
        }
        return ret;
    }
};

analysis

  • time complexity O(n)
  • space complexity O(1)