sample code

gistfile1.txt

#include<bits/stdc++.h>
using namespace std;

// please not at any time we will keep elements in the map called mp whose index lie between i to j.
// Initially both are 0 so only first element is added in the map

int solution(int a[], int n)
{
    set<int> st; // to store all the elements to find number of unique elements
    for(int i = 0; i < n; i++){
        st.insert(a[i]);
    }
    int len = st.size(); // length of unique elements

    map<int, int> mp; // map to store key as elements and values as their frequency
    mp[a[0]] = 1;
    int ans = n; // initial answer will be number of elements
    for(int i = 0, j = 0; i < n && j < n;){
        if(mp.size() == len){ // if we have at least spanned through len elements
            ans = min(ans, j - i + 1); // update the answer to minimum of current answer and length of span,
            // elements are spanned from (i - j) index
            if(mp[a[i]] == 1){ // if single entry
                mp.erase(a[i]); // delete it
            }
            else{
                mp[a[i]]--; // increase the frequency
            }
            i++;
        }
        else if(mp.size() < len){ // if we have still not collected at least len elements
            if(j < n-1){ // if there is score of collection
                j++;
                mp[a[j]]++; // include it
            }
            else{ // we have reached last element and need to break the loop
                break;
            }
        }
        if(mp.size() == len){ // update answer here too
            ans = min(ans, j - i + 1);
        }
    }
    return ans; // returns answer
}

int main() {
    int a[] = {7, 5, 2, 7, 2, 7, 4, 7};
    int n = sizeof(a) / sizeof(a[0]);
    cout << "Array: ";
    for(int i = 0; i < n; i++){
        cout << a[i] << " ";
    }
    cout << endl;
    cout << "Answer: " << solution(a, n);
}