import java.util.HashMap;

public class Min_window_substring {

public static void main(String[] args) {

String s1 = "timetopractice";

String s2 = "toc";

String s = solutions(s1,s2);

System.out.println(s);

}

static String solutions(String s1, String s2){

String ans = " " ;

HashMap<Character,Integer> map2 = new HashMap<>();

for (int i = 0; i< s2.length(); i++) {

char ch = s2.charAt(i);

map2.put(ch, map2.getOrDefault(ch,0) + 1);

}

int mct = 0;

int dmct = s2.length();

HashMap<Character,Integer> map1 = new HashMap<>();

int i =-1;

int j=-1;

while(true){

boolean f1 = false;

boolean f2 = false;

//acquire

while (i < s1.length()-1 && mct<dmct){

i++;

char ch = s1.charAt(i);

map1.put(ch,map1.getOrDefault(ch,0)+1);

if (map1.getOrDefault(ch,0) <= map2.getOrDefault(ch,0)){

mct++;

}

f1 = true;

}

// collect answers and release

while (j < i && mct <= dmct){

String pans = s1.substring(j+1,i+1);

if(ans.length() == 0 && pans.length() < ans.length()){

ans = pans;

}

j++;

char ch = s1.charAt(j);

if (map1.get(ch) == 1){

map1.remove(ch);

}else {

map1.put(ch,map1.get(ch)-1);

}

if (map1.getOrDefault(ch,0) < map2.getOrDefault(ch,0)){

mct--;

}

f2 = true;

}

if (f1==false && f2==false){

break;

}

}

return ans;

}

}