Untitled

import java.util.*;

public class MinimumWindowSubstring {
    public static String minWindow(String s, String t) {
        // Initialize variables
        int n = s.length();
        int m = t.length();
        int[] arr = new int[256];
        int i = 0, j = 0, minLen = Integer.MAX_VALUE;
        int leftBoundary = -1, int rightBoundary = -1 , count = 0;

        // Populate the hash map with characters of string t
        for (int k = 0; k < m; k++) {
            arr[t.charAt(k)]++;
        }
         
        // Start the sliding window
        while (j < n) {
            // Expand the window by including characters from s
            if (arr[s.charAt(j)] > 0) {
                count++;
            }
            arr[s.charAt(j)]--;
           

            // When a valid window is found
            while (count == m) {
                // Update the minimum length and boundaries
                if (j - i + 1 < minLen) {
                    minLen = j - i + 1;
                    leftBoundary = i;
                    rightBoundary = j;
                }

                // Shrink the window from the left
                arr[s.charAt(i)]++;
                if (arr[s.charAt(i)] > 0) {
                    count--;
                }
                i++;
            }
            j++;
        }

        // Return the minimum window substring or an empty string if no valid window is found
        return leftBoundary == -1 ? "" : s.substring(leftBoundary, rightBoundary + 1);
    }

    public static void main(String[] args) {
        String s = "ADOBECODEBANC";
        String t = "ABC";
        System.out.println("Minimum Window Substring: " + minWindow(s, t));
    }
}