Codeforce - They are everywhere

#include<bits/stdc++.h>
using namespace std;
#define pb push_back
map<char,int>mp;
int ans=100002;
int main()
{
    int n;
    scanf("%d",&n);
    cin.ignore();
    string s;
    getline(cin,s);
    list<int>ls;
    for(int i=0;i<n;i++)
    {
        int temp=s[i];
        ls.pb(temp);
    }
    ls.sort();
    ls.unique();
    int i=0,cnt=0,left=0,counter=ls.size();
    while(i<n)
    {
        if(!mp[s[i]])cnt++;
        mp[s[i]]++;
        while(mp[s[left]]>1)
        {
            mp[s[left]]--;
            left++;
        }
        if(cnt==counter)ans=min(ans,i-left+1);
        i++;
    }
    printf("%d\n",ans);
    return 0;
}