Count distinct elements in every window.txt

https://practice.geeksforgeeks.org/problems/count-distinct-elements-in-every-window/1

vector <int> countDistinct (int a[], int n, int k) {
    vector<int> v;
    
    unordered_map<int,int> mp;
    unordered_map<int,int> ::iterator itr;
    for(int i=0;i<k;i++){
    
        mp[a[i]]++;
    }
    int key=mp.size();
    int count=0;
    v.push_back(mp.size());
    for(int i=0;i<n-k;i++){
        
       if(mp[a[i]]==1){
       
           
           key--;
           
       }
       mp[a[i]]--;
       if(mp.find(a[i+k])==mp.end()||mp[a[i+k]]==0){
           
           
            key++;
           
       }
       mp[a[i+k]]++;
        v.push_back(key);
        }
        
    
    return v;
}