3)Count Occurences of Anagrams - (sliding window)

Given a word pat and a text txt. Return the count of the occurences of anagrams of the word in the text.

Example 1:

Input:
txt = forxxorfxdofr
pat = for
Output: 3
Explanation: for, orf and ofr appears
in the txt, hence answer is 3.

Example 2:

Input:
txt = aabaabaa
pat = aaba
Output: 4
Explanation: aaba is present 4 times
in txt.

c++  implementation:

int search(string pat, string txt) 
	{
        unordered_map<char,int> mp;
        int k = pat.length();
        int m = txt.length();
         
        for(int i = 0; i < k; i++)
            mp[pat[i]]++;
            
        int count = mp.size();
        int ans = 0, i = 0, j = 0;
         
        while(j<m)
        {
            if(mp.find(txt[j])!=mp.end())
            {
                mp[txt[j]]--;
                if(mp[txt[j]]==0)
                count--;
            }
            
            if(j-i+1==k)
            {
                if(count==0)
                ans++;
               if(mp.find(txt[i])!=mp.end()) 
                {
                    mp[txt[i]]++;
                    if(mp[txt[i]]==1)
                    count++;
                } 
                i++;
            }
            j++;
        } 
        return ans;
	}

time complexity: O(n)
space complexity: O(n)