Smallest distinct window

       
        
        Given a string 's'. The task is to find the smallest window length that contains all the characters 
        of the given string at least one time.For eg. A = “aabcbcdbca”, then the result would be 4 as of the 
        smallest window will be “dbca”.

        Example 1:

        Input : "AABBBCBBAC"
        Output : 3
        Explanation : Sub-string -> "BAC" 

        Example 2:

        Input : "aaab"
        Output : 2
        Explanation : Sub-string -> "ab"

        
        

        Code
#include<bits/stdc++.h> 
using namespace std;
int main()
 {
	    string s;
	    int i,j,n,k,mn=INT_MAX;
	    cin>>s;
	    n=s.size();
	    
	    unordered_map<char,int>m,m1;
	    for(i=0;i<n;i++)
	    {
	        m1[s[i]]++;
	    }
	    k=m1.size();
	    i=0,j=0;
	    while(j<n)
	    {
	        m[s[j]]++;
	        if(m.size()<k)
	         j++;
	        else if(m.size()==k)
	        {
	            mn=min(mn,j-i+1);
	             while(m.size()==k)
	            {    mn=min(mn,j-i+1);
	                m[s[i]]--;
	                if(m[s[i]]==0)
	                 m.erase(s[i]);
	                i++;
	            }
	            j++;
	        }
	        
	    }
	    cout<<mn<<endl;
	    
	 
	return 0;
}