Smallest window in a string containing all the characters of another string 24-09-24 POTD.cpp

// https://www.geeksforgeeks.org/problems/smallest-window-in-a-string-containing-all-the-characters-of-another-string-1587115621/1

class Solution
{
public:
    string smallestWindow(string s, string p)
    {
        vector<int> mpp(26, 0);
        for (char ch : p)
        {
            mpp[ch - 'a']++;
        }
        int req = p.length();
        int i = 0;
        int j = 0;
        int n = s.length();
        if (req > n)
            return "-1";
        int minSize = INT_MAX;
        int sp = 0;
        while (j < n)
        {
            if (mpp[s[j] - 'a'] > 0)
                req--;
            mpp[s[j] - 'a']--;
            while (req == 0)
            {
                int currSize = j - i + 1;
                if (currSize < minSize)
                {
                    minSize = currSize;
                    sp = i;
                }

                mpp[s[i] - 'a']++;
                if (mpp[s[i] - 'a'] > 0)
                {
                    req++;
                }
                i++;
            }
            j++;
        }
        return minSize == INT_MAX ? "-1" : s.substr(sp, minSize);
    }
};